Does anyone know how much bhp i can put through a standard escort diff? Ive got about 200bhp, and i think it ll need uprating. What parts will i need (what ll break first)?

apart from a "slippy diff" if your so inclined i would'nt bother, the cars that light you will get wheel spin B4 damage.

Is it worth fitting a limited slip diff then do you think? ive found one for sale at £275 is that a good price or should i look elsewhere?

You might get away with it if you don't have sticky tyres, but generally the Escort axle is only recommended to 150bhp. The first part that goes is the cross pin in the diff centre leaving you with no drive!

The only way around it is to fit a LSD. The Quaife one will cope with 250bhp and mine gives no problems with 200bhp and 9" slicks. Be wary of plate diffs since they need the ramp angles changing for a light car like a Locost otherwise you'll have terminal understeer