Thanks for the replies folks.
What I meant with the cables was that I have tried both s-video and composite cables, both of which are well screened. So interference is ruled out. I have also routed the signal through my Yammy avamp and up-scaled to component output to see if that helps, still no joy. As I mentioned before live recording is perfect, no interference at all. Only when the HDD spins up the interference occurs. I have the latest sky box. My mate's old sky + box does exactly the same so it rules out a faulty box. One work around I have is when I record from sky+ to my Sandisk vmate and then play the recroding back through the DVR it's fine, but that sort of defeats the purpose of having the dvr.
I've asked archos support twice now and they haven't replied, they are worse than useless. Looks like my only option is to wait and get a HDDrecorder and route the signal through this, a right royal pain in the a**e though