Wethers do get fat even on grass, all that hanging around. I don't think Ryelands are suitable as hogget, better by the end of their first year. It works best with primitives which grow slowly and don't tend to grow fat.
We have, over the years had a variety of butchery and packing types so we have shopped around until we have found a lovely butcher who cuts how we want then vacuum packs, and he also makes sausages and burgers to our recipe, with ingredients I provide. It's worth paying that bit extra to get it done how you want it. From a different butcher I have also had the horrible big careless fatty chops (we have in the past had other breeds) so I understand your disappointment. After all that time, you have something unpalatable to eat, and your sheep gave his life for that.
Sounds as if you will be eating him yourselves, or you'll put off future customers (unless you know someone who specifically likes fat lamb - most people don't). Cook the chops very hot which crispifies the fat and gives flavour (and makes a huge mess of your grill!) then cut the fat off on the plate. For the big joints, try finishing them off very hot too so the outside is crisp. The belly I would make into burgers, and remove the fat first.
For future kills, find a better butcher, who is happy to discuss and give advice about what you want. Have a look at what he has on sale to point out just what you want back, and ask how it will be returned to you. Our butcher collects from the abattoir on the same day each week, so we ask him what day he wants us to take the sheep in, so they can hang for a bit there before he picks them up. He vacuum packs and freezes except the burgers and sausages which come back in bags as I request, so I can transfer them to meal sized portions then freeze them myself.
It is also a good idea to, if possible, go to the butcher before he cuts the carcasses and ask him to show them to you. Not all butchers have the facility to do this, but if yours is willing then he can give you good advice on how to improve your husbandry to make a better carcass. He can point out where you may have a problem (such as too much fat) and he will appreciate knowing what breed they are before he starts. Some butchers may have no experience of, say, primitives so will appreciate your input too. We usually have our chops prepared as 'Valentine chops, where the small chops from primitives are part cut through then opened out to make a cute double, heart shaped piece. Primitive gigots tend to be comparatively long, so the butcher may suggest that he cuts steaks from the top, so the joint will fit in a pot (we have a long covered roaster specifically to accommodate a full gigot). Our sheep don't have belly either, and the ribs are tiny and lean. All variations in breed.
And Cambee, no you've not been thick, you just didn't know and now you're asking to make things better next time. There could well be people on TAS who use the same abattoir and can recommend a good butcher - it's well worth the search to find one.