If you want to try some gloryholes there are some at the Locker Room sauna in SE11 (Kennington)
There are cubicles there with lockable doors and holes between them, so you can suck or play with as much cock as you want through the holes.
Usually it's men only, but once a month they host a mixed Bi night (currently on the THIRD Thursday night of the month.)
It is a very friendly atmosphere and the guys were on the whole pretty well behaved. It's a Bi night, so you can expect to see guys playing with other guys as well.