Thank you all for all your input. Ollie is so much better this morning thank goodness, it's so upsetting to see them not well.
I have noted giving the yoghurt and will be getting some later today. I think I will make it a daily dose, as I mentioned he will try and eat anything when we are out walking either on or off lead. He is especially keen on tissue, paper, cardboard, sheep and horses poo and even rabbit poo to name but a few! Hopefully the yoghurt will help him fight off any 'nasties', you need eyes in the back of your head when he's outside!