Whistler is now fine, we never came up with anything wrong really but after a dose of antibiotics he has settled down but it was 3 - 4 weeks.
I have changed his feed to Natures Best and touch wood its ok now. What with that and the slug episode three lots of samples (wee, pooh & bloods) nothing was found wrong except for loose (to be polite) grey frothy pooh.
So Best Wishes to all sick doggies and I hope they all get better quicker than Whistler (and £480 our bill!) cheaper.
Viv