Frustrating isn't it!(posted 8605 days ago)I'm in more or less the same position at present and although I haven't got any legal advice for you I would say to really study this web set - it's a mine of valid information.
Regarding the MIG - I was also refused a copy of this so have just written back quoting the latest Civil Procedure Rights under which they have an obligation to show you all documentation relating to the case, (see answer to question DLA how to proceed). Have you also served them with Subject Access Rights? (see under Data Protection)- I've yet to see what they will show for me but at least it shows that you know what you're talking about to a certain extent and they cant just bully you into paying up!
Good Luck anyway!