There are an increasing number of connections sold through LCY, for pax it's no real issue to walk past baggage claim, up the escalator, and through security again. A word with the queue marshal (the entrance to the security area has recently changed) can have you stepped past any long queue, although recently I've found I'm walking straight up to the scanner anyway (a new bottleneck and queues seems to be developing at bag drop/check in). Bear in mind that although UK-LCY-Europe can connect without recheck, Europe-originating pax require a security check.
I always despair to find, looking around LCY somewhat lost, pax (invariably non-British) who have been sold ticketing of say AMS-LCY, then connecting across London to a LHR-LAX several hours later. You have to wonder what sort of corporate travel agent (because they are invariably business travellers) sets this up.