Having been prompted by another thread, I just thought I'd report back on this, given that 18 months have now passed.
So I asked our vet for advice on whether to cull Bonnie for her own welfare, since she had a long-term weeping sore and we were due to start tupping shortly. To my surprise, he said "look, you've only got a small flock, and I think you're managing her welfare just fine. Even commercially speaking, she's your most valuable ewe, and gave you your best ewe lamb last year. So, if she was mine, I'd have her tupped and then manage her through it.
I had some misgivings about this, but we went for it anyway, and to my surprise, in mid November 2016 she must have ejected whatever foreign body was causing the recurring abscess, and everything cleared up completely.
She then went on to give birth to a cracking tup lamb, who is destined to become our new stock tup.
OK, it's not all roses, since she scanned empty this year, and will probably now be culled (especially since we now have her son in the flock), but on this occasion, the gamble paid off
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