Well, technically, John Innes, but it does rather depend on what you want to grow in them. Acid lovers will need ericaceous potting compost, others will find loam based John Innes too rich for their taste.

For annual bedding plants I would use any peat or peat substitute based compost as it contains a small amount of nutrient and a wetting agent. If it is for a long term planting then a John Innes, soil based compost is best. It makes the pot more stable, holds nutrients longer, re-absorbs water and it seems to be less inviting to the vine weivel. Our old friend, Alan Titchmarsh favours a multi-purpose compost mixed with John Innes No.2.

These days G Centres sell compost for about every occasion if its for a special plant, some with added nutrients and water retaining gel.....but you pay for it!

The above is really good advice

Thanks for all your comments.

I watched a TV prog where pots and hanging baskets was filled with a very dry high grade of peat. I've not used or seen this one before unfortunately i couldn't see the name on what they were using.

Being it was a large bag thought it might save some pennies, also give a good flowering result.

Hanging baskets are fine with multi purpose potting compost (although a lot of them are lumpy rubbish now). John Innes is loam based and too heavy for hanging pots. The trick with baskets is keeping up with the watering - in full sun in summer, they need watering twice a day, and I feed mine about every 3 days with a liquid mixed into the water. They also need watering when its raining - I see my neighbours giving me a very old fashioned look when I'm standing out there with my 2 litre bottle, slowly trickling the contents into the basket in pouring rain. And then they tell me it looks lovely and they don't know how I do it...

Just a tip.

I fill and freeze my ice tray daily, then put the frozen cubes into the baskets.
Stops me having to lift a heavy watering can above my head also i dont get soaking wet.

Thanks for all your help on the soil.