My key will not go ino the ignitionon my Jaguar s type.

i am sure you jiggled the steering wheel in all positions while trying, if the wheel lock is stuck, the ignition key won't open.

Dealer or certified locksmith

Do not tear into it your self serious damage will result

Your key can wear down from use. I had this happen on a 2001 Mustang. I took the key to lock smith & he was able to dupicate a good key. If you can wiggle the key & finally get it to start, it's either the key or your tumbler.