Boro,
Had this when I left my last job after being hunted by a (and probably only serious) competitor. Left on the Friday, started new job on the Monday.
Old company tried to take me to court for breach of contract. Courts chucked it immediately as I was no longer under their contract. They appealed, it was chucked again.
Two fingers I say.
Bottom line, you are only under contract while being paid by said company and that includes all benefits. Once that ceases, so does anything in the contract, including any new stuff they added in the months before you left.
If you need any more help, PM me.
Cheers
Ian