Welcome to Flyertalk and welcome to the BA forum.

The best way to handle this is to ask for an Original Routing Credit for the Manchester flight and any other cancelled services. Now because you put in for a refund it may be that is at this point tricky, ideally you ask for a refund on the rail ticket and related costs but at least initially don't ask for a refund. There is an ORC guide elsewhere in this forum, I would give it a go, there's nothing to lose here.

Ultimately it's just the way that BA runs BAEC, their game, their rules. Clearly it's not in their interest to hack people off in the way that has happened to you. Hopefully this forum will give you some good pointers to get your Bronze / Silver status back again.