I had the same issue as you, knew there must be farm butchers about reasonably local but struggled to find one.
In the end I got my stuff from Tarelgin Farm Butchers down Ayr way. They do free delivery locally and luckily enough my sister stays in Kilmarnock so was able to get it delivered to her place. Got a few pieces from them to date, you phone them early in the week and got it delivered on a Thursday or Friday.
The phone call is alway interesting, the woman who usually answers the phone is a bit of a character, in a good way, if she’s not sure what you are looking for the butcher will get shouted over and you can explain to him exactly what you are after, seemed to have a reasonable understanding of what I wanted and can’t say I was disappointed.
I’ve also tried to use Greenhall in Blantyre, this place sell animals literally reared in the fields outside the shop and although very pleasant and helpful, said they couldn’t provide a full brisket due to the way the carcas was split at the slaughter house. I don’t understand the reason for this but I’m not a butcher so what do I know. They do rear wagu cattle tho and I’m sure you could get plenty of other cuts to order, just not a full brisket it seems.
If you come up with anywhere else I’d love to hear about it