Lo-Cost from LHR? What is everyone smoking?
I'm afraid it's only a matter of time. LHR must be the only major airport in Europe which DOESN'T have lo-co flights (But I'm prepared to be corrected on that if some are already sneaking in). Harps, Orange Tails, Air Berlin, German Wings and Vueling (owned by IAG) are everywhere else.
EZY has bases in CDG, ORY, FCO, MXP, MAD and SXF (soon to be THE Berlin airport); it will soon have one in LIS and it is always talking to CPH, ARN and AMS (where it already has a massive number of daily flights in and out). It should have one in BRU but the authorities there stubbornly insist on their high charges. Keep your eyes on MUC.
RYR mostly avoids major airports - for the moment.
Yes, it's only a matter of time.