rachylou : Sorry, I should have been clearer in my original post, the vet's advice regarding the roughage was a separate point, he didn't state it was connected to the blood, other than checking the rabbit for piles - hence the extra roughage, just to be sure.
As for sharing the same hutch, that was a question I raised with him before we accepted the GP. He said it was OK. The concern regarding the GP getting enough of the right food is addressed by making sure when they're fed, the rabbit doesn't push him out of the way. As it happens, the GP is always the first there, the rabbit takes his time.
Babsie : they chase each other occasionally, as if in play, but there never seems to be any aggression. After 18 months together I'd expect to see some form of behavioural pattern or injuries. It's only in the last few weeks that the blood has appeared. The previous hutch was smaller so any territorial disputes etc would have occurred sooner, surely. I particularly expected it as the rabbit had the hutch to himself for about a month before the GP arrived, yet seemed to accept him straight away. If one wanted to keep out of the other's way, they've far more room to do so now. As for the extra vit C, he acts as normal & the vet said he was OK on the last check up, some months ago. This is what puzzles me : no previous fighting nor evidence such as clumps of fur or blood (until 6 weeks ago), both are thriving as normal, neither overweight at the expense of the other, and the 3 week gaps between the blood findings.
Jacks-Jane & Amy104 : have to confess I'd not heard of Bordetella Bronchiseptica; I've done a quick internet search & the GP doesn't show any of the symptoms currently. I'll be taking him to the vets as a result of the advice kindly given on this forum, so I'll quiz the vet about it at the time.
I do trust the vet, never had any cause for concern regarding the 3 cats we've had, a hamster & these 2 boys. My brother's used the same vet for 2 dogs & he's never raised any issues, either. It has a good local reputation but, as I said in an earlier post, maybe a second opinion would be beneficial.
I thought I'd done my research before getting these fellas, I've always had the view that if you take on an animal you do your best, despite the bills etc. . . beginning to feel a complete ignoramus!