Wrightflyer - I'm envious - I'd love to be doing my hour-building again! It's such fun.
My basic advice is to avoid burning holes in the sky flying something expensive just for the sake of it. At this stage in your career in Aviation it's very tempting to page through the 'Groups' section of pilot magazines and websites with an eye on the flashiest aircraft for hour-building. Hey, we all do it! I did it! At one stage I even considered getting my MEP before my CPL so I could do some hour-building in a Twinstar!
The reality is that you'll get to fly the more expensive aircraft later on, but all the value of hour-building is found in the handling and cross-country flying and planning skills you'll accumulate. You can do that in a 30 year old Cessna 150! Whatever you do, make sure your hour-building involves many long trips all around Britain.
Aircraft Grouping Ltd looks to be a good deal, especially on the C152. There's also a chap on here who hires out C152s. I'd look into his rates. Talk to your local Flying Club and approach them with a proposal to do a large number of hours on their most underused aircraft. They might bite. The only problem with F;ying Clubs is they rarely let you take an aircraft away for more than a day without requiring a prohibitively high number of minimum number of hours be flown per day.
But if you're really clever you'll buy a share in a group. It's definitely the cheapest route to many cheap hours. It's a bit more hassle and there is the stress of not being able to sell your share later on. What about something like this:
FLYER Forums • View topic - £1200 PA38 Tomahawk Share - Bristol or a similar group in your area?
Good luck.