dave,
take it to these guys at slacks creek which should be just round the corner where you live.. They reconditioned my coilovers in the past and were real good. Clunking sounds normally means a leak somewhere. Get them all checked out and reconditoned if neccesarry. They will come out brand new. around $137 per corner well worth it
http://www.shockreco.com.au/
They have undergone a change of management since I was there last but have been told they are still good.
let us know how u go.
cheers
jon