Your view of the Cayman is tainted by the fact you bought a lemon without doing any checks though, you have to admit. The engine issues are well documented and easy to keep an eye out for, and don't affect anywhere near as many cars as the internet suggests. That said, clearly the M96/M97 isn't perfect as Niki says
OP, if you considered the Pug, any thoughts on a decent hot hatch? Golf, Megane, Leon? Not sure on your budget, but if we're assuming around £20K (including some mods) and you like Jap stuff then a GT86 with forced induction would be an incredible choice of car. Ultimately not as rewarding as the Cayman nor as quick as the TTRS, but certainly a dramatic enough car and plenty of things to do to it for a smaller budget than the Germans.