GET IT! GET IT! GET IT! ;)
Bargain if you ask me, I paid nearly £500 for my 50w 4104 2x12, you're mate's looking for £350? BUY IT NOW!
I use a HotPlate with mine, all you need is the HotPlate (obviously) and another speaker lead. Put the speaker lead in the amp's "Speaker Out", then plug it into the "Amp in" on the HotPlate, then plug the speakers lead into the "Speakers out" of the HotPlate. Mine lives on top of my amp.
The 800's didn't have an effects loop, so if you have one, it's been modded.