I agree with roddycm, if the tup doesn't have that stink which Shetland tups often wear in abundance, then the meat will be OK. We have found that if we try to send our sheep to the abattoir near to Christmas they don't have space for them as that is their busiest time. Being a primitive he won't put on much condition over the winter, so I would send him off straight after Christmas as soon as the abattoir reopens. It would be fine to keep him with the ewes until then, as once they stop cycling, he will lose interest, whereas if you put him in with his wether friend then he will keep trying with him, just in case he's turned into a ewe while they were separated - that might keep him stinky.