Originally Posted by jim739
Providing you have the time, you're able to exit Frankfurt Main and walk over / get a car transfer to the F terminal. I've done this before without problem.
Totally correct. You exit Frankfurt immigration, then walk through the airport until you reach Zone A - this may involve walking through a weird tunnel a bit like the one at LHR connecting the terminals and the tube. Exit here at street level and walk literally 2-3 minutes to your left. The next building along has the words 'Lufthansa First Class Terminal' on the side, and in you go.