I decided to experiment on sunday evening and bought myself some Tesco Extra Special gammon steaks and some coconut milk...
After marinating for two days I cooked on up today and it tasted delicious, possibly a bit too salty but that can be worked on.

1 table spoon of Skippy Peanut butter 
1 tea spoon of Olive oil
1 table spoon of lemon juice
1 table spoon of water
1 table spoon of coconut milk

Grab the gammon steak and run a knife up and down it not cutting all the way through but just into the flesh, then spread the paste liberally over it, it should spead as easy as margarine, if not add some more water
Once you have it pasted on then add any powdered seasoning you wish (if you wish, its perfectly fine without!)
Stick it in a tub and put in in the fridge for a couple days.After that cook it however you so wish! I fried mine in some olive oil for a tasty explosion