It's not just bareback that transfers things. Its good practice to have a MOT every so often and make sure everything's fine and safe.
I've just looked at the local hospital or walk in centre for GUM clinics and gone in there. Mentioned i was also a swinger and got the full testing, including a blood test, just to be sure. Gives you peace of mind too. I know a number of people who get the postal tests though, and it does seem to cover things.