To renew your suspension...
www.buypartsby.com:
R19 Wishbones including the bushes and the ball joint for under £15 per side.
Most Motorfactors:
ARB bushes (or from reno if you prefer)
Eurocarparts:
Track rods/arm + Track Ends - circa £40 perside (these are a Renault Clio 16v item but from others who have used them it seems they work perfectly on the williams track also). Febi/Bilstein product.
From Renault:
Top Mount Kits approx £28 per side
Williams Struts approx £48 per side
Springs:
Option 1 Buy from Renault: Approx £160 the pair
Option 2 Buy from aftermarket specialist who will make OEM 'copied' springs circa £100 the pair (search for a post by mark ritchspeed - he mentioned this many years back - from memory he also mentioned what company could make them).
Option 3 Buy Low mileage 172 (NON CUP) Springs from people selling on cliosport (they are the same as the Williams springs denoted by two white dots) - Normally go for £30 - £50 the pair
Option 4 Buy Low mileage 172 Cup springs from people on Cliosport (denoted by one white and one yellow dot). Slightly stiffer than Williams OEM springs (5-10%) and slightly lower too (3-5mm) - Normally go for £30 - £50 the pair