I personally think the show will be better off to just end with Harry. After all as Gavin and others have stated, he makes the show what it is, and it is partly his format.
Whilst I am gutted about his departure, I can't help but feel the glory days of the show are over. It was at its best when it was in some graveyard time slot and was more of a quirky, geeky 'cult' programme compared with it's current mainstream bloated state.
Dave Lamb was in an episode of Miranda, a thing on Dave
That was a pilot of a programme starring Alexander Armstrong. I assume it didn't get a series, but it was in a similar vein to the Rhod Gilbert thing on BBC1