Update:
This morning Eddie didn't seem himself still so I booked him into the vets. He's just gone in with Elvis for company.
His poos are no longer squishy but they're smaller and some of them are oddly shaped. He's still trying to eat hay but gives up after a few strands. I offered him a few snapped in half pellets and he ate those and didn't seem to have a problem. I know pellets in no way replace hay but at least he's still interested it food.
All the best! It is not quite easy when you as an owner know that something is not quite right but there are no 'easy' obvious symptoms. Fingers firmly crossed; please step in with syringe feeding top support - smaller poos mean reduced food intake. A few more pellets won't replace all the hay he is not eating.