They're definitely not Aberdeen Angus. AA's are polled, for one thing, and a much better shape than these girls, for another.
To us, Welsh Blacks are more beefy than these ladies, hence we suggested WB out of dairy cows.
There are long-legged and short-legged Dexters. I just saw a Dexter heifer in the ring at Lanark, but she had horns like a Shetland (at least, like Rosemary's Shetlands, I've never seen any others) not upturned like these ladies.