DIY Doctor UK DIY Forums

The background is, I decided to clean my attic tank while replacing the ball cock there. Unfortunately - like all these well intentioned jobs - there is now a complication - apparently some debris seems to have lodged in the WC refill unit and it keeps overflowing.
WC make: Laufen Pro
Cisten fill unit: Geberit.
Does anyone know how to disassemble the Geberit unit to try and clear it ?
Thanks, Ben