Having owned a cheap flexwing for years, and had great fun in it, fixed running costs are roughly:
Annual permit: £200-£300
Cheap farmstrip hangerage: £300 pa
Odds and ends: £100 pa
Insurance: £250 pa
Fuel: £15/hr
So, roughly plan on £1000 per year as basic ownership cost, then about £15/hr for the flying. Add in probably £50-£100pa for membership at your local club, maybe £50pa to keep your charts and airfield guide up to date, and £5/landing when you visit other airfields.
Reasonable second hand aeroplanes seem to start around £3000.
Types to look for (if going for cheap second hand): Mainair Flash 1, Pegasus XL, Pegasus Q, Raven-X. There are others, but any of those are a good cheap starter machine.
Reckon also on a couple of weekends a year of "fettling" - just routine fiddling and maintenance outside of your actual flying time. It's also well worth owning (or at least knowing where you can borrow) a trailer: even if you keep it at the airfield, it's nice being able to take it off places (or retreive it after weather traps you in the back of beyond) so if you don't have one, budget for sticking a towbar on your car as well.
G