You are quite right; the use of composted wood chip or bark would be used as a mulch to retain moisture around your plants. I wouldn't buy new multicompost but you could use the spent multicompost from your tubs and baskets. As for farmyard manure can be bought from farmers either already rotted or fresh in which case you would need to stack for a while or mix it your compost heap to speed up the breakdown of you plant waste. Just be aware that you can also buy rotted farmyard manure from garden centres but it often comes already mixed with peat to make it go further; so I would say this is the one to avoid.

The trouble is that 'compost has two (at least) meanings. It is the term used for the multi purpose stuff sold for potting. This may be peat based or not depending on your preference. However, it is also the term used for the decomposed remains of organic material created in a heap, or other suitable container.
So, when someone is adding compost to a plant, it could mean either of these. Usually though, it means the material from a compost heap. Multi-purpose compost is not really that much use as a planting medium in the garden.
Mulch, as Jimmy says, is the term used for covering the soil with a layer of organic material of any kind.
Well rotted manure is even harder to define. The field behind us has a heap of material from the local chicken torturing sheds. It could be called well rotted manure as it is full of droppings and the organic material from the bedding.
Farmyard manure is the bedding straw and droppings of the animals which sleep in it. When properly stacked it rots down to an amorphous mass in which the individual components are no longer discernible. Not the easiest stuff to get hold of in the middle of a town or city.
Personally we never use animal material on the garden as we find the stuff, even when well rotted still contains huge numbers of weed seeds.
Again as said, you can buy bags of sterilised manure from most garden centres.

In addition to Jimmy's answer above, I'll add something that defines the terms mulch and compost.

Mulch means anything which is laid over soil and left there - organic ones could be bark chips, composted manure, your own garden compost, or previously used potting compost from pots, leafmould, cocoa shells - even the leaf litter layer in woods and forests behaves like a type of organic mulch. Then there's the inorganic mulches, often used for decorative purposes, like slate, shingle and so on, which don't break down over time and don't contribute to the health of the soil.

'Compost' as a term can be confusing, because it's used for the stuff you make in your own compost heap as well as the stuff you use in pots. The trick is, putting an adjective in front of it, so for container growing, you need potting compost - this could be John Innes or multi purpose or a mix of the two, along with specialist types such as seed and cutting compost, ericacious potting compost, even houseplant compost, which is also potting compost.

Other forms of compost are not intended for use in pots, and these include composted manures, soil conditioning compost that you can buy from some municipal facilities, and your own home produced garden compost. Garden compost can be used in pots ONLY if its been produced using a hot, aerobic system - if its produced from a cold, anaerobic heap, then its not suitable for potting purposes. Hot aerobic compost is made by frequent turning, which causes the heap to heat up sufficiently to kill most pathogens, and can be added to potting compost mixes, or applied to the soil, either as a mulch or dug in - cold anaerobic is the opposite, its just chucked on a pile or in a bin and left to get on with it - but it still makes a useful addition to garden soil, once its ready for use.

oops Owdboggy, posted at the same time...

At least we agreed!

Thanks all, very interesting and re Owdboggy's point re weeds, I live in a very damp area where weeds are verdant and thrive so guess local farmyard manure no matter how well rotted will be recycling some weed seeds when used? I see large buckets of chicken manure (pellets) in the hardware stores which seem to be a hit with local gardeners so imagine that is an alternative to fm yd manure.

The only problem we have with chicken manure pellets is the conditions in which the hens are kept. To get enough material to make the pellets they need to collect an awful lot of droppings and the only way that can be achieved is where the hens are packed into a small area, as in the chicken torturing barns just along the road from where we live.
Another point is that Farmyard manure (ie humus) does not feed the plants, it feeds the soil which then has a lot more 'life' in it which helps plant growth.

As Owdboggy says, chicken manure pellets don't add humus to the soil, they just break down and offer nutrients direct to plants, but its the soil you need to care for, then plants do better anyway. Buy your composted manure from the garden centre - its usually mixed animal manure rather than just horse manure, but it comes without weed seeds and is ready for use straight away. That improves the soil by increasing bio diversity, making it more welcoming for plants to grow in. The only exception is if you're going to be planting root crops like carrots - they fork in manured soil.

One could say a lot more about humus, if one was pressed.
For example, if a soil is deficient in one of the trace elements, say, Boron, or Calcium, then adding humus will not correct the imbalance. You would still need to add those trace elements to the soil in the form of soluble fertiliser. What humus does is feed the soil organisms which break down the mineral content of a soil into forms which plants can absorb.
Want more?

Thank you all, guess that's what Monty means when he says "feed rage soil, not the plane" it's about creating maximum growing conditions for plants. Oh I know about the chicken torture chambers, used live near a Bernard Matthews factory and saw pics of turkeys used as footballs. Just had our local horse fair in my town and could glimpse the dogs for sale in the backs of vans being kept out of view of the Inspectors if there were any present. Doesn't make pleasant thinking material.