Ours are butchered by a local chap, who collects the carcases from the abattoir in his refrigerated van when he is going there anyway, so that's not a problem for us and doesn't cost extra. We haven't sold to the general public since the recent regs came in, but when we did I took all the deliveries straight from the butcher to the customers, in insulated boxes (supplied by the kind butcher). I wonder if that would be different now - because you can send meat through the post and it's not refrigerated then.
If you are selling from a freezer at home, as well as not keeping your domestic food in there, you will have to have it checked out - temp and so on, by presumably Trading Standards, who will want to know that you are selling from home anyway.
As for pricing - all I can say is be proud of your produce and sell it for a good price. I tend to look in the top shops, then take off a tiny bit, but of course they sell by cut, not for a half or whole carcase, so your top cuts will look cheaper than the shops because there will be all the cheaper bits in too. Have a look online too - I'm staggered by what some people charge for their meat, and they are clearly selling it
Another way of looking at it, is ask what you want and see what people will pay - if you target the right people they are prepared to pay a premium for mutton, which is a gourmet choice. Some people will not buy, but others don't flinch