When I said I checked the glow plug I did also check the actual seal on the plug, I also tried different plugs (all Enya No.3's) and no change throughout. I've been using 20% castor, 10% nitro the whole time, so the oil is the right stuff.
BTW, I think it's a late engine (def. got an ABC). I'm wondering if the loud popping/banging noises from the exhaust which I have been hearing (or had heard ) have anything to do with this. As for the warranty, I want to avoid sending it back as much as possible since I have to pay the postage costs (mail ordered you see). I'll try it again tomorrow morning, I've left the plug out overnight on the window ledge so the engine can air nicely. If it still won't give anything, back it goes.