I agree about the seatbelt position! I was very surprised that it wasn't height adjustable, and it was driving me nuts as the belt kept slipping across my neck. I solved the issue by raising the height of the seat which helped a lot, and then I bought a really cheap seatbelt clip from eBay which simply clips over the lap part of the belt, and you slot the shoulder part of the belt under the protruding tang when you do up the belt. It alters the angle of the shoulder part so it's more comfortable.
I was initially concerned that it may affect the safe operation of the seatbelt, but it's so flimsy that it would simply pop offin the event of an accident, and the belt would tighten as it's supposed to.