I cleaned him out last night & the smell has gone, he seems a lot healthier and cleaner.
I think he was scared and peeing all over himself but he is a lot cleaner now, plus he started using the hamster potty for weeing immediately.
So all good - thanks for the help guys.
I've bought some dried yogourt, fruit treats & dried carrots in place of the wet food but ill give him the odd bit of fruit/veg every now and then.