There are remote terminals (used by FR) and a main terminal. Note sure which one KLM UK would use.

If you are connecting onto a Ryanair flight, I doubt if you can transit to the next flight as FR doesn't even interline its own flights. You'll have to reclaim your bags and then recheck in. FR wants a change fee on top of positive fare differences in their favour (but nothing for you if the fare difference is in your favour).

The remote terminals require use of a people mover (automated guided bus).