After reading this thread I started to look for clinical trials in the UK that I might volunteer for - I contacted the Beckley Foundation as they were involved with BOL-148 trials www.beckleyfoundation.org .
I got a response from them today - thgey're not currently doing any trials but said that there are two clinical trials recruiting participants for psilocybin and cluster headaches: One at the Rigshospitalet’s Neurobiology Research Institute in Copenhagen, Denmark (Contact: Gitte Moos Knudsen, +4535456720, gmk@nru.dk), and one in West Haven, Connecticut, USA (Contact: Emmanuelle Schindler, 203-932-5711 ext 4335, emmanuelle.schindler@yale.edu; or Christina Forte, 203-932-5711, ext 2526, christina.forte@yale.edu).
Thought I'd pass this on in case anyone wants to volunteer
Phil