In reply to lynda: Hi Jon, thanks for your post.
Currently he has had quite a few tests which have shown no signs of tumour (whihc is promising). This means we still don't know what is causing the bleeding. The next step is an endoscopy, but we have to wait for either a suitable blood donor to come forward or for him to make enough blood to cope with the anaesthetic.
Does anyone have an indoor cat or knows of anyone with an indoor cat (preferably in the Glasgow area) who might be willing to allow their cat to be a blood donor? Normally this wouldn't be a problem, but as it happens my cat has a rare blood group (B) which is proving difficult to find a donor.