ok check this out clicky
is this likely to be the same for the ST round about (i know this page is talking about a paxo vtr but never the less)

and will a induction kit and a cat back exhaust give a power increase without the flexi pipe? i dont actually mind if it stays the same as long as it doesnt go the other way - on my old car it lost power after i got a cat back fitted (didnt have an induction kit however) although it was a 1.2

Powerflow are as good as the guy you get fitting it which tends to be not that good. They go for sound rather than actually designing a decent system that gets the most out of your ST. Many many people really dont rate them at all (me being one of them) but people have had them and been happy.

Re power gains, you should get a power gain but it wont be vast. I reckon changing the flexi really will help a lot because someone else had just an induction kit and a Milltek flexi and had 165bhp whereas I had that and the cat back and had 168bhp (rolling roded at the same time on the same rolling road).

as pinky says... especially bout the "fitter" bit.

i personally hate powersapperflow.. but hey.

Which induction kit can you recomend? I'm not too technical but hear that a cold air feed is better.

Where can I get one and a flexi pipe from?

Depends how much you want to spend really! You can pay about £90 for a K&N 57i (probably cheaper off eBay but you know what I mean), £200 for an enclosed carbon filter or DIY (buy some hose and a filter).