If you can up your budget to around £700 then I'd suggest the BC Racing coilovers we offer, which we've supplying and fitting for the last 4 years with positive reviews, it's a great kit...
Pm replied to just now...
The Cobra system we do at £425 will replace the middle and the rear, and will also make a good replacement over the OEM system, we can supply and supply and fit here in Leicester...
We offer the full range of Eibach spacers, the 20/25mm combo can be seen here - http://cougarstore.co.uk/index.php?main_page=index&cPath=1_18
Email or call us if you need any more info...