Company is called GSR Engineering. Visit the forum
www.performance206.com in about two weeks and you'll have an idea of what's going on with the engine.
Cam I'd say minimum of 8bhp, max of 15bhp. It's impossible to tell until we actually get one reprofiled, but the cam has quite a bit to give- especially on the PSA 8v engines.
Induction kit is around the £150 mark

seems a lot but unlike all the shit like K&N (I used to have a K&N 57i) it actually works. We did 4 separate tests of induction on the 206 when we ran it... first time was the standard airbox, car was pumping out 62bhp as it was. With the K&N 57i it dropped to 58bhp (quoted factory standard), with the Pipercross from a Fiat Punto 1.2 16v (had one lying around) it was 61bhp... and then with the GSR kit it was 69bhp. I also had mine remapped that day, got a nice round 74bhp.
I'll keep you posted on here regarding what we find. The head looks to be pretty solid anyway, very good for standard. The PSA induction and cams appear to be the weak spots on the TU 8v engines.