Lamb prices always rise in the run-up to the Abrahamic religious festivals Easter, Ramadan, Passover etc. Also fluctuates with supply and demand there is a spike in May/June as the old season lamb runs out and the new season aren't forward in any numbers, then the lowland lambs come onto the market July/Aug hill lambs start to appear on the market Sept/Oct you can see the effect on the price graph. You can see the prices and seasonal effects for all types of stock in Farmers Weekly.
Two main different styles of butchery, traditional UK which tends to cut in straight lines and leave meat on the bone and Continental where they tend to cut the muscle off the bone. IMO the continental joint is easier to carve but doesn't cook/taste as well.