when to scarify

You could dispense with the scarification and just put an autumn lawn treatment down, which usually includes a mosskiller. Disadvantage is that, when the moss dies, you'll have bare patches.
Otherwise, scarify now, spike all over with a garden fork, apply lawn sand or similar.
With either method, In spring, scratch up any bare areas and put some grass seed down.
Feed the lawn monthly during April through to September - higher nitrogren means less moss. Unfortunately, drought like conditions in summer will increase the level of moss when the weather gets damp again, and the other thing that makes moss get a hold is, obviously, damp, shady conditions.

Bamboo... thanks for this info. We haven't had a lawn in years but the deal with the neighbour is we keep his lawn looking nice and in return we get the land to grow the veg. I was wondering what to do when...

Scarification, for preference, usually done late September, followed by spiking and topdressing, for future ref, Moongrower, but its not impossible to do it now

Don't compost what you rake out as it will spread the moss around when you spread the compost.

Please clarify.. is it okay to still use autumn lawn treatment in late October ?
Most packets say "till September". Thanks.

Ah, of course, forgotten that, Terratoonie, you're absolutely right, they do say September, so no, it's not alright. I think it might be alright to use proper lawn sand though - if you can get it and check the packs.
Where did September go...

Thanks. Where did September go ?

I can't believe its October - I suppose September felt more like August, it was so lovely, and now feels like end September - I surely am getting old, it's whizzing past...

:o)

My lawn is now so wet that just walking on it causes damage but at least after that long dry spell its now green.

the lawrn just up the road from me has at last turned from a light yellow to green ,and from a distance it looks nice, it is lined with twenty foot laylandi with thick exposed roots and the coulor is produced by moss there is not a blade of grass ,there used to be.

thanks for the advice everybody. Just one more things : what is lawn sand exactly - just everyday sand ? And what does it do?

No - its a product that was once readily available but which has fallen out of favour a bit, so can be difficult to find at garden centres. It is still frequently and commonly used by greenkeepers, though but might not be available to the general public. Again, let me repeat I can't remember exactly what the formulation is, it may be that there's some feed in it, which would mean you can't use it and seed at the same time.
Just looked it up in an old book - product used to be called Velvas, but recommended application is not not later than September, even if its still available, which it probably isn't, so forget I mentioned it at all, sorry. Leave the feeding till next year now, and again, not if you're reseeding patches.

I buy ready mixed 'Lawn top dressing' its sand peat and loam I do it every autumn after scarifing and brush it well in. On my clay I find it really makes a difference.

That sounds like the sort of thing I mean by lawn sand, but I don't think you can use it this late in the season.

No I dont think you can I do mine in September.