Further update - have exchanged quite a few emails with these two now - they seem 100% genuine, really friendly, and just working out a time to meet (potentially this evening, if not then Monday lunchtime). Keep you posted but am pretty excited to be partaking in my first REAL threesome (which means where the girls are properly into each other, unlike the normal "girl 1 does a bit while girl 2 sits around looking a bit bored, then they swap".