32 kg is a reasonable weight for that age, especially if he's had a bad start in life.
The deciding factor in whether you send him for slaughter is whether he is fat or not . Only you can tell, but if he is pure bred, then he most likely is fat at that weight.
However, if he is a lot smaller than the rest, I would not put him in at market as he will spoil the others if put in with them, and may not get a good price if sold on his own.
If you have the option then I would say he's definitely one for the freezer. He won't take up too much room and Welsh sheep are usually delicious.