I tried to leave Ostend an hour early on a VFR plan about 4 months ago and was told no departure before flight plan time. So spent ten minutes cancelling existing plan and refiling. (Nb the plan came up on their system about 3 seconds after I pressed submit on SkyDemon).
Only after I got home did I realise that (of course) I’d simultaneously cancelled and refiled a GAR without giving the 4 hours notice but havent had a knock at the door yet.