So here is the reply from the club: "When teams play away games, they request a specific allocation of tickets for the away area. For cup games, teams can request extra space, which leads to us having to displace season ticket holders. When Manfield requested they requested the full allocation we could offer and assured us that they would sell out, as such, we allocated them the full amount requested. Once sections are allocated for away, we are unable to recall them in events that the team do not sell out. As such, Mansfield failed to sell out, which resulted in large empty areas."
Bonus points for the swift reply, but points lost for not actually answering my question. I still don't understand how they could have segregated the fans without leaving empty blocks - particularly 223 which, as I've said, is not separated in any way from Club View.
So I've replied asking them this: "Block 223 runs directly into the Club View, so away fans cannot be seated there. Why was I displaced from an area that cannot be allocated to away fans?"