I have exhaust, cats, plenum, and intake. cars with this sort of mods in the US and already a technosquare reflash have seen + 13-15 WHP.
Moreover, on a n/a car which will eventually go FI, it's just a small step towards it
If you read the links provided, you might have realised that when eventually I want to go FI, I'll just need to re-tune. And yes, at the moment, all FI systems come with some sort of piggyback ems, such as the unichip used by APS. Thing is, they are not as good as the UTEC... Plus, doing it this way, you can just get yourself a Tuner version of the kit you want and save money that way...
Oh and £685 is closer to £500 than £1000...