Hi Caroline, my Beltex x Txl ewe has also two such lumps, but not in her fleece, one on the neck just behind the head and one on her side/belly, just under the fleece line. The second one is raw and she keeps rubbing it. I have sprayed loads of plaster tar spray to get it to heal but no good. She is fine, no flies on it... I also think they are bites - maybe horse flies? they seem to be very bad this year?
She has had these for over four weeks now...
I haven't found anything in my vet books, and she is eating well, seems to be feeding her lambs and doesn't look bothered by it in any way...