Update from sender - 6 months after posting this on here, I thought I would update in case any other people come across the post. I went to the Dr (with the support of a few truly lovely people on this forum) and he took me seriously. He prescribed me fluoxetine - its main form is as an anti-depressant, but apparently it can also be used to lower libido, particularly in men. We tried 20mg for 3 months and now it has been 40mg for the last 2 months. Initially I felt very hopeful indeed about this. However, irritatingly, it has not had any affect at all on either my frustration or on the unwanted erections.
Blood tests showed high testosterone, out of normal range, but not serious enough to consider hormone therapy (according to my GP) - something like the top 0.5% of men or something like that. There's a whole load of other things they measure, but the long and short of it was that yes, my testosterone levels are very very high for a man in his 30s, but 1 in 200 men will also have levels this high (god knows where they are?! it is hard to find any help if you google / search for anything to lower erections. usually its the opposite - you just get loads of stuff about viagra etc etc).
So now, I'm in a limbo with everything and feeling utterly sick of it. I am still single and this is definitely exacerbating the problem, and I am still hopeful that the fluoxetine will somehow magically kick in and give me some relief from the frustration. But it seems like this has not changed in the last 6 months and anybody with any advice at all - it would be very gratefully received indeed.