How to arrange Greater Occipital Nerve Block (GONB)

I've looked through all the posts on GONB on OUCH and I know nearly everything there is to know about it, except how to arrange it. I know that they are a relatively simple procedure which can in theory be carried out by a GP or GP surgery nurse, but my impression is that they are best carried out by an experienced and specialised practitioner. The name 'Dr Juana Marin' comes up in a couple of posts, but my problem is that whenever I have attempted to contact Queens Square the phone is never answered, voicemails and emails are not responded to, and the only time I've ever had any joy is by sending an online fax. The last time I tried, because I hadn't seen Dr Matharu for about ten years, I couldn't self-refer, I had to go via my GP, and wasn't offered an appointment until 3 and a half months later (my episodes currently last up to 3 months).

I have also found that the Headache Service at St George's Hospital (recommended on an OUCH post) does also offer GONB, but again I can't self-refer. Does anyone else have experience of this? Would it be quicker? I would really like to have a solution to this.

Thanks in advance.