It has been a problem as long as I can remember and the first time I crossed was over thirty years ago.
These days I don't even ask and plan to fly round, even if I'm landing at LHR, because there is nothing passengers hate more than being put into a tight orbit to hold. Especially if they don't travel well.
Have you considered routing via Burnham - Ascot-Thorpe - OCK. Even less likely to result in a hold is WOD- Ascot-Thorpe- OCK, ATC seem to like these routes.