I live in Somerset and i will be sending my shetland X castlemilk moorit wethers off next month without hard feeding if I can.
We have very good grass, and I know most would hang on to them for a bit as they are smaller than your average sheep BUT they are in good condition and as my husband won't eat them I prefer a smaller joint. Also one of them is a horrible butty thing and I don't keep trouble for the fun of it!
If you think they are ready, send them in!
Having said that, they certainly aren't going to say no to a little extra feeding