Not sure fella - we get quite a few joining through the Thames area nowadays. Easy for us to get you up to 3000 feet if you are going SE. (Unless KB/LC are busy then we need the levels)
Generally easy to do: but we need to get a strip from the Asst, get a DM done, and get a strip over to the TMA S. Just becomes tricky when really busy with other higher priority tasks.
The only one I had on Sunday was some poor lady who had a FPL in, and we got joining clearance only for her transponder to fail and have to return to TR.
A real bummer as TC_LTN handed her over under a RIS primary only, I got her through the zone and as it was still not working she was refused entry to the Airways system. (last month we had a dep of LCY who got turned back by the French as the Mode C was inop - despite West Drayton/Swanwick approving it).
I hope she got it fixed.....