Does the bit of plastic trim which goes round the artermarket head units slide over the stereo before you fit it, or does it clip in afterwards...thanks.

If you mean the bit you can see in my car (see here http://www.briskoda.net/forums/t33276-you-beauty.html) then it clips on afterwards. The HU is fitted into the DIN-slot behind it, then this goes on top. But I don't know what the specific part number is just for the trim surround.

The dealer fitted everything in the new car; looking at the invoice (no free lunch!) the part number was AZ0600003 "Double Din Octavia kit" (doesn't specify which Octavia) and cost was 70 euros before tax, say about 50 pounds. They also needed a canbus adaptor, part number STC857CAN "Plug and Play Canbus Anal" (honest, that's what it reads!).

Thanks, this is just a cheap piece of plasic trim that fills the hole around the new head unit. I didn't want to get the unit in and find the trim should have been on first.

Its a Fabia vRS