Can anyone horsey people tell me approx how much livery would be for just a stable & grazing, on a DIY basis?

Not a horsey person but this http://www.equine-world.co.uk/buying_horses/cost_horse.htmmight help. I think it depends where you live too

It varies a lot, but usually between £60 and £120 per month, dependant on location and facilities. London woudl be more, I am guessing.

You should ring all your local ( or however far you will travel to ) livery yards and ask their prices. Then go and visit the yards and speak to as many clients as poss. Even better would be to have a yard recommended to you. Yards vary greatly, not just in price, but in clientele, care, security, ease of turn-out, good rides, hacking etc. You should find out how often the fields are rotated and rested, how many to a field, is it mixed sex. It would be great if there is a school you can use - will that be xtra? Will the livery owners turn out/muck out/feed if you are unable to and how much? Will you be provided with access to a secure tack/feed room? What is the policy re illness/accident/vets if you are not there? Make a list of these sorts of questions and away you go :)  Don't forget to have a contract drawn up too- very important. HTH

Around here, from £15 a week upwards, depends on facilities.

Try your local council, they may have something.