Final update - we've just been the vets for a check up and he said he's amazed at how well Alfie has recovered.
He bounded into the surgery, practically dragging me along, ran straight up for a fuss from the nurse and eventually I got him to settle down by the chairs. He did try and back away when he first saw the vet but when he was offered a fuss he soon went for it, so I think the vet is forgiven!
I was told he had 10cm of his bowel removed which in the grand scheme of it isn't a huge portion so he shouldn't be affected. The vet said there is a small chance of recurrence but doesn't think it'll happen in this case because there was no apparent underlying cause, although when I mentioned Alfie had always had fairly sloppy poo he said this was possibly a factor (his poo is now 'normal' following the op).
So we don't have to go back, the wound is healing brilliantly, his fur is growing back and he's just as energetic/happy/crazy/bouncy/bitey etc since before he was poorly. He can play in the garden supervised for short periods and can start going walkies again from next Monday.
All in all a brilliant result, and I'm sure Alfie will be pleased to know his feeding routine can get back to normal, which started with a Bonio when we got home!!
Thank you for all your kind words and thoughts, it's been a rough few days but hopefully now it's behind us.
P.S There was no charge for them sending off the claim form either.