Used to have to do it along with Turkey/Chicken/Duck/Beef because everybody else wanted gammon. My own fault for trying it one year and they decided it was better than anything else I made ratbags.
I would boil it with spices - random selection of clove, pepper, star anise, cardamom, caraway, bay, juniper, orange an lemon peel, etc (essentially gin ingredients) after changing out the saltiest first boil water, then roast it with bitter orange marmalade, more spices and random fruit (plums, apples, pears, rhubarb, whatever I had plenty of).
In terms of what goes with it, there's the traditional parsley sauce and boiled potatoes version, gravy and cauliflower cheese/steamed swede/carrots/peas and bread sauce - or what I think is the best, chucking a load of split peas into the second cooking stock and making pease pudding (which I'd eat tons of in preference to the gammon, as whilst I may very well make a nice one, I don't actually like it - or pork as a whole - that much).
Unfortunately, I made a second error when I mentioned to DP one year that I used to do gammon. His bloody eyes lit up, so I had to make it that year and he asks if I can do it every year since.
I've compromised and make it for New Year now.