Ive got one.
Doesnt use much more fuel, unless you drive at 5000+ rpm everywhere then it does drink a fair bit more. I recently had a run up the M40 and M6 back to the north west and averaged 34mpg. With the original ECU I got 44mpg. I was tanking it 100+ on the M40 though and averaged 65mph!
My normal daily drive to work is 1/2 motorway 1/2 A roads and I get the same mpg now as b4.
I personally havent told the insurers as the only way theyll know is if they take the ECU out (which is a b**ch of a job) and read the part no., or hook it up to Renaults diagnostic machine.
I remember reading that R-sport say the ECU mapping will cope with a k+n filter and ktec exhaust. Ask R-sport when you order it.
I dont think you can remap the ECU as I assume its the same hardware as the standard ECU but with a different mapping. And I guess Superchips wont have a remap for the R-sport ECU.
I guess if youre going to do major engine/breathing work then get a dastek unichip. This costs fair bit more though but can be remapped live on the rolling road to take account of mods.