Meister R's and BC Racing do coilovers in the region of £500-£700 I believe (running BC Racing coilovers myself, difference is phenomenal in both handling characteristics and image).
Springs are available from a fair few dealers on here; talking 20, 25 or 30mm drop. Most commonly used would be Eibachs I think!
I've had dealings with Zmanalex, CS and Chilli Red and have had great service from them (think the majority of members would agree with me there). Give them a PM, see if they can help you out!