Thanks for the replies everyone.
The Remend drops and Optimmune seem to be doing the trick and Coco's eyes seem much better. I am also using some artificial tears from Superdrug which help too (and much cheaper than the animal version)
I have found the Remend drops online for about £11 for a 10ml bottle compared to the same price for 3ml from the vet, and the Optimmune seems to be generally under £30 online, so that is much better.
My vet has given me a prescription for 4 tubes, so I think we will go back and get Coco checked over and then I will be holding out for a 6 month prescription. That way it works out at just under £200 compared to £408
I usually don't bother if there is a bit of a difference in price, but since this is an ongoing medication and the difference is £38 a tube it is well worth it!