maxalt
Suggest for the future you might try a quick call to Operations and your company specialist in negociating slots with Central Flow. The idea being direct communication might achieve desired result and reduce your apparent frustration with the system.
Otherwise its haggling time at the bazaar on frequency as Clearance Delivery/Ground contact London FMP who contact Central Flow.
The GA and Air Taxi Operators figured this out some time ago and call directly to Central Flow using mobile phones!
The Central Flow Helpdesk can be contacted on:
+322-745-1901
Include PPRUNE User id with actual callsign for best results and feedback!
Familiarisation Visits available on request for Operations Staff,
Flight Deck & Cabin Crew.
Central Flow - Brussels, Belgium