If you can manage to free up 8K now, but are not sure you can keep freeing those kinds of funds in a few years time, then you might simply want to forget about it. Here's why:
Just keeping sufficiently current to fly a regular SEP (nosewheel) requires around 12 hours annually. (The legal minimum is actually 12 hours every two years.) That's going to cost around 2000-2500 UKP minimum annually, unless you make an upfront investment in a share or even your own aircraft.
That type of currency is nowhere near enough to fly aerobatics safely and up to a reasonable standard. If you want to be reasonably current on aeros in a basic aeros aircraft such as an R2160, you have to count on at least 30 hours annually. For advanced aeros machines such as a Pitts or Extra, maybe at least 50 hours annually just to stay current and safe for your landings. Remember these are twitchy taildraggers.
If you want to participate in competition aerobatics at the level that these aircraft are able to provide, you may need to fly in excess of 100 hours annually to have any chance of competing. And these aircraft cannot be rented for ~200 UKP per hour anymore...
You do the math and decide whether you can afford that kind of money and whether it's worth it to you - after all you can only spend it once.
I flew competition aerobatics at the Standard level in an R2160 for a number of years. This cost me close to 10KEUR annually for 40 hours of flying. The R2160 got me consistently in the middle of the pack, but to have any chance of winning in that class I'd need to upgrade to a more capable machine such as the Cap 10C or a Pitts. Upgrading would easily double my annual cost, and I decided that that just wasn't worth it.