TBH Jimmy contact AVO direct 'cos I'm fairly sure they're not £400 from AVO unless they've put their prices up alot. (seem to remeber a mate getting a pair from them a year or two back for around £60ish each). AVO's are easily rebuilt and I believe quite reasonably at AVO whereas I don't think Koni's can be rebuilt and spax(rubbish) deffo can't be rebuilt and wont last through the build without leaking
For springs go to Eibach. There UK place is near Leicester Nr A5, cant think of the address at the moment. Get the springs from there - should be reasonable prices and they're good quality with good chip resistant finish.
BV.