The vet just called, it wasn't a blockage at all but an intussusception, part of his small intestine had gone inside another part of his small intestine and the blood supply had all but been cut off, so the folded in bit was dying, which explains the blood passed this morning as well as everything else. Apparently this can be fatal very quickly if not treated.
The vet said he's removed some of the small intestine but quite a small section, and has reattached it ok. He was concerned initially about reattaching as it's quite close to the end of the intestine (cecum?) but he's done it and thinks it should heal up OK. I was still a bit paranoid about the chicken but the vet said it wouldn't have been the cause, more often than not there is no determinable cause and it's just 'one of those things'.
When he called he said Alfie was just coming round and seemed to be doing really well although we have to wait for the next 24-48 hours to be sure he'll be OK. The vet will call again in the morning to let me know how he's doing and whether we'll get him home tomorrow or Monday.
I'm so glad he's insured as I dread to think what the cost will be, but I've read that there's up to a 25% chance of recurrence and presume that further occurences won't be covered. All I can do is hope it doesn't happen again, we don't have the kind of money it'd take to 'fix' this.
In the meantime we're missing him like crazy, even with a 5 and 7 year old the house seems so quiet. I want my boy home with his needle teeth and wiggly bum!