Just pick one area of London and market the hell out of it. Make sure there is a variety of food styles available every night.
Short of actually flyering local homes, does anyone have any ideas for cheap & effective local advertising? I've got some Facebook ads running, but targetting more locally than just "London" doesn't return many people.
There is a similar site to yours already launched in London, fairly well established called HouseBites.co.uk - have you studied their model? Mike from HouseBites gave a talk at YCombinator London about 1 or 2 months ago. Did you see this talk? There is a video floating around somewhere.
Some of the logistical issues were discussed which may give you some assistance on for Meal Mogul.
I am also working on a different yet related project EatSocial.net (see blog.EatSocial.net) - think meetups in restaurants. Would you be interested to meet for a chat? I am based in London and would like to hear more about Meal Mogul.