Mike hi, I don't have this problem because mine hasn't got the flapper valve fitted although Nev has sent me one which is sitting on my desk at the moment. Instead I intend to fit a solenoid to the FIP shortly which means a kill cord can be fitted. Mermaid do the solenoid and a little bracket to make it fit.
There should be a wiring diragram in the P22 Owners manual on my web site, help yourself to a copy
Nev is in Edinburgh somewhere but not exactly sure where, however he refurbishes P22 for a living and is a mine of information. Think this is one of his.