In that case it sounds like your reasonably serious about giving it go
£200 is a tight but dooable budget to get going on...and with some careful purchases you'll find some good fun and competitive racing too!
I'd suggest you visit the club your going to race at BEFORE you buy anything...see it first hand...ask to see what people are running...ask the people there for their opinions, see what it's like in the flesh...websites and spec's on paper are one thing...but seeing the real thing first hand is another completely...you'll get what we're talking about a bit more then, and might even meet some people with some bargains while your there...
IMO the 2nd hand B4 suggestion is much closer to where you should be looking than the annsman stuff...except maybe the X-Pro which looks to be more race spec than any of the others. That would then allow you to grow into it. Racing regularly you might out grow the smacker in a few weeks and be looking for another car that goes better and is tougher, you'll be breaking stuff to begin with!
I started out with a simliar budget, a B4 and entirely 2nd hand bits and bobs....and gradually spent more money as I got better!
Mostly though...enjoy!!!!