i wouldnt personally say they are not good as they have produced some great cars just quite a few people have had issues with them and for the money you pay you would expect better.

you dont really need go to a renault specialist to tune the engine as most of it is good old fashioned tuning eg cams, headwork etc its a shame your so far away as id advise you to come up to stoke (am motorsport).

as i said id firstly get a good set of brakes and coilovers along with a set of lightweight alloys on there and strip it right out this on its own will improve your lap times.
Then to start sort the breathing out on the car full exhaust system including manifold, good induction kit and port match the manifolds this combined with a remap will see some good gains. then you can enjoy the car whilst saving for cams throttle bodies etc