As someone who has just started down the buggy route, and blown my budget way out of the water - consider the following:
- Old tech doesn't mix with new tech very well (i've just learn't that in a practical way)
- What kind of buggy are you looking at and where will you race it? 2WD and 4WD have very different handling characteristics depending where you race them
You can save a whole load by going down the second hand route and applying a little patience. Remember whatever chassis you buy, spares are a major consideration and you are going to need them - so factor the spares into your budget.
£200 is certainly possible but you'll need patience. Had I employed patience, I would have saved a fortune and bought my Caster(s) only (2 chassis, 1 is a brushless RTR, the other 90% aluminum, spares, RC kit and NIMH batteries) with £104 remaining for lipos!