I'm in a somewhat similar position although I'm not in the UK. I've spent a good while "under the stone" working on my product and I do have some great relation

I'm in a somewhat similar position although I'm not in the UK. I've spent a good while "under the stone" working on my product and I do have some great relationships with investors/customers, but I don't have any strong connections with technical folks so it's a bit lonely at times. In all fairness though, I've been so busy lately that networking isn't a top priority. If I were you I would try to find a Meetup and invite myself, get out of your comfort zone. I've had a lot of success doing that and it's one of the better decisions I've made in the past year.