thanks for all the comments guys.
Reasons I went for the clio box, was firstly due to not being able to source a R26 box, as no point putting a 225 box on without the diff, and more importantly, i wanted to keep the much shorter ratio's of the clio box.
I have driven a megane r26 (girlfriend has one) and although it suits the megane, the gearing feels a little long.
I am hoping the clio box can cope with the power, as i would ultimately like to put a diff in it and use that.
Then tune the engine to work with it, ie: run a turbo that has power higher up the rev range.
And i have to agree with shakey, in gear acceleration with the clio box must be a fair bit quicker than the megane.