Cheers for all the advice team!
Just to clarify, I'm o.k with changing pedals normally, I know they go different ways
. And there are handy arrows on them with "Tighten ->" so it's really hard to get wrong
(but always good to check the simple things first!)
Warming them up sounds like a good call, but they've got a ridiculous shiny gloss finish and I might make a real mess of them.
I think i'll try to fashion a vice out of whatever I can find in the garage (cheers for the inner tube suggestion, definitely a good call), then I'll try putting them back on the bike, and if there's still no joy I'll probably getting in touch with one of your guys who offered the use of an actual vice! Cheers all