You're in for a long and exciting journey. David Layne is a great contact for a start. So is Nick Fenton. Both had Dads in the PoW camp that your Dad was in. I would recommend you google all the bits of info that you have - if like me you'll find lots of nice surprises. Looking up your Dad in my trusty 'Footprints on the Sands of Time' by Oliver Clutton-Brock, I see the following in the massive PoW index:
Bliss, EJ, Sgt, 7 Sqdrn, Aircraft N3716, Stirling, Shot down 19 May '42, Mannheim, PoW camps L1 (Barth) L6 (Heydekrug) and 357 (Fallingbostel), PoW number 796
These little snippets will keep you occupied researching ... so many avenues await you.
Good luck and wait to hear of your progress. By the way, my Dad was Flt Sgt R C S Hancock (later Warrant Officer). And he was at L6 and 357, after a stint at L3 before they made it an Oflag, when he went off to Lithuania with the NCO fraternity in autumn of '43.
Pat