For aerobatic stuff you can start by looking
here. Unfortunately there isn't really anything that fits your budget. The closest is a S2A for £7500, but it doesn't say what size the share is. The One Design looks very interesting if you want something cheap to fly, capable, and single seat. Again unfortunately the share price is out of your budget and I've no idea what the maintenance costs would be. Also something to bear in mind is that with low numbers of shares you are more exposed to cash calls for unplanned or unexpected maintenance.