Just about all the other approach or TMA controllers at TC have (actually are required to have) validations on different approach or area sectors, thus a bit of variation.
Maybe semantics, but not quite correct from a TMA perspective. North, South and Midlands (the majority of the sectors) controllers, just like EGLL controllers, are not required to do another sector. The fact that the majority of them do on goodwill (for no reward) is the reason the Ops room functions at all from a TMA perspective.
The three sectors, but especially North and South offer a huge variety within themselves. The other 2 sectors, East and Capital are extensions - east used to be a bolt hole for a first validation if there were no training places available, but this is no longer practiced as it has been proven that it is very difficult to cross train onto North or South as they are much more difficult. The idea being that we are a band 5 unit for a reason... Capital has never been offered as a first validation as it is too sporty (when busy) and does not reflect the ideal practices a controller should display - too much performance based controlling is required when the sector kicks off (fairly seldom in the past couple of years, but it will go that way again when traffic picks up).
'Tis a shame about the lack of EGLL bods with regard to cross validation, as the chap on my watch who does another airport loves the variety 9and the freedom the other airport gives hime with a nice big RMA)!