To add to Vlad's bit, on top of the TMA (above FL155/FL175 depending on area) is TC Capital, working just 4 levels mainly upto FL210. FL180 and FL190 are used for Stansted/Luton arrivals inbound to OCK from the South or West. Trying to get descent inbetween these tracks is near impossible, so it would have to be FL200 until 10 AFTER MID, at which point you will be in the Seaford (S18) sector at LACC, and no straight ins possible if on r/w08.
At the moment you stay at FL150 for so long, as the LL ins from Hurn come down to FL130 at Hazel on track OCK, and for KK its FL130 by GWC as you probably know, so its all about finding that gap to drop thro, and the lower you are, the less gaps we need to find
