Demdempster - yes, it has an internal analogue tuner just like a VCR, so you can record one terrestrial channel while watching another via your TV tuner. The man in JL is wrong. It is quite poor though, as I mentioned before, with the picture noticeably sharper and richer in colour via my (cheap) TV's internal tuner - and that's even after looping through the Pioneer.
As far as I know the only way you can record BBC1 analogue terrestrial (say) and watch Sky is if your second scart output from the Skybox (the one that used to go to the video) goes to a spare scart socket in your TV (or loops through the old VCR to the TV in my case), and you select that scart input on your TV. If you're recording Sky on the Pioneer you have to select the L1 AV channel on the recorder, so you watch terrestrial via the TV's tuner as usual.
I think I've just managed to confuse myself as well as everyone else!
PS in testing this, I just set the Pioneer to BBC1 terrestrial and recorded for a minute or so. I didn't realise that it would take the programme title from GuidePlus - very nifty!