It's entirely possible to get a fully working machine for £50, if you are looking at unpopular machines, and / or don't mind driving to pick them up.
I normally spend between £150 and £250 on machines, however that is including courier delivery, normally at about £75 (with Speedlink transport).
I'd say to pick a machine that you think you will enjoy, not just a machine that is 'cheap'. I've made that mistake before and have ended up bored to tears by them. Did you like older machines with lower jackpots? Have you ever played club machines? (I find that clubbers tend to make more sense for home use, as they have much longer 'cycles' than a normal pub machines).
Fired off an email to MAC Automatics this morning who is a local company working with machines etc in the hope they might have something 
I used to buy from local suppliers, but they've either stopped dealing with the public so much now, or charge 'trade' prices for their machines, which are way higher than the usual second hand price on eBay e.t.c.
Best of luck though
Edited by Bencrest, 07 November 2012 - 02:35 PM.