He has cream cheese and some cheese for training.... thanks for the tip
Just posting again to say that the last couple of mornings he's been fine, no bile! I'm thinking it was down to not eating for so long that one time, an honest mistake (that I feel bad for) but won't make again.
Perhaps the string from the ropey tug just irritated his empty tum a little. I've given him a Bonio before bed btw, but the box is almost empty and payday fast approaching so will be stocking up on the suggestions for treats given.
Thank you all