Renting might be difficult. Many companies will not allow solo rental and therefore you are stuck with the H/C restriction in competition.
Almost all the pilots who compete are owners or own a share. The choice of aircraft probably dependant on your budget. If you have a few £100K then an Extra 300 would be a good choice.
The cheapest is probably a Pitts, but unless you have an S1T then you are going to be aircraft limited at intermediate and certainly Advanced. The monoplanes such as one design, Laser and Extra 230's can perform well at intermediate and advanced, but are more expensive.
This will give you an idea of prices.
Aircraft+Equipment-for-sale
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