I don't think checking with e.g. Heathrow helps, with VFR flight plans. They can get lost anywhere, and if they aren't lost they may not go anywhere useful except departure and destination.
I am starting to think that the best way to file VFR flight plans is to fax them directly to the departure and to the destination i.e. two faxes for each one. Then one is able to telephone each end and ask if they've got it.