Cheers for that Andy, if I may call you that
Rather than clogging up any storage on this board, there's a link to the service manual
HERE 11 meg download
Somewhere, I found a more complete manual of about 111 pages, but I've temporarily lost it
But since it's smaller, I've attached a copy of the circuit diagrams to this post; this id from the D75, rather than the D755 Post Office 16A Varient