I went through them on another matter 3 years ago - also with the Halifax. Once you get a case no, the process is quite easy, and they do write back - just takes a bit of time. You can refer to the Room Service precedent too.
If nothing else it causes grief to the brokers who must spend admin time completing detailed forms for FSO, obtaining phone info etc. Their compliance teams don't like it one bit, and they get measured by no. of complaints too! - so worth doing. I'm at stage 1 - asking for my certs for now.
I used to be with Halifax but don't use account now. Find Squaregain much better in terms of prices, sizes, markets & variety and you get money to transfer your holdings.