um, sorry for rainig on your parade,
but you wont gain 10bhp from skimming the head and polishing the ports!!!
a nice polish definately WONT help with power....
and for £650 i could go to town on your head....think of a fully flowed head (about 35hrs work!), chemically cleaned, skimmed, repainted, 3 angle valve seats....the lot!
That WILL give you the 10-15BHP you were looking for. and coupled with TBs and a cam you could well be looking at a 150bhp......even more if you really tried hard.
My 1.6 MK1 XR2 is running about 150bhp with one of my own heads.