Well if you're free lancing you're not on a 142 program. All 61 says is that if it's not under 142, only 20 hours counts. But good luck walking into a sim.
Since you're posting in the NA forum and show a London location you may have to go through our TSA. The training center I work for spent days trying to get an F/E into a sim for recurrent. The TSA wouldn't give their OK because his F/E cert didn't have a type on it like the pilots in the group. For those that don't know, the FAA doesn't give types to F/Es, only class ratings. Turbojet is good for a DC-8, DC-10, A-300, B-747, B-727 or L-1011. You now know more than that TSA person.
To instruct in a sim you don't need any ratings (you're not flying a plane), you just need meet the qualifications for a CFI and you need to be on the Training Center's paper work. Again, not set up for free lance.