My year old cockerpoo isn't that interested in food, he only has a dental stick in the morning and has a mix of dry food and chicken wet pouch at night which he will only eat with a lot of encouragement. Also his poo is firm in the morning any after that is quite runny. What should I do ? He is well in himself and enjoys his daily walks and chases the ball.

First thing to do is make sure he is getting enough fluids.
Diarreah can dehydrate a dog very quickly.
If he isn't too keen on water try mixing a splash of puppy milk in with it.

If diarreah lasts for more than 48 hours you need to get the dog to a vet straight away.