I'm not sure how it is in the UK, but I'd be really surprised if what you need can't simply be purchased from a store. Look up jock itch and ringworm, which are what these in-your-crotch fungal infections usually are. I'll grant that your particular case might be severe enough that a prescription-strength cream would do better, but if you're facing additional weeks of waiting, I'd strongly encourage you to pursue the non-prescription route. I went to the doctor the first time this happened to me, and the "prescription" was, "Go to the store and buy jock itch / ringworm cream." I was kicking myself, because like you, I'd been suffering for weeks. The cream had it gone in a couple of days.