You don't need a mentor. You need to start doing interesting things.
When you're doing interesting things you will meet people who are motivated to help you.
People won't take much of an interest in a person who is looking for a mentor but not doing anything.
Stop overthinking this. Establish relationships with other entrepreneurs near you. You can shoot the shit with them when things are good and when things are bad. You'll get introduced to other interesting people.
One day maybe you'll meet the fairy godmother you seem to be seeking, but if you don't you'll have made a start and know some interesting people. And, crucially, you'll be doing something.
Edit: Just saw that you're based in London. Go to the meetups and hackathons and python dojos and LRUG etc.
Thanks georgespencer, that got me realise probably I'm just planning stuff that doesn't go planned.
I was going to meetups and LRUG, but in most of them I just found people that talk and don't do, so I decided I stopped going until I roll out something or at least do some customer dev.
Thing is with this approach I won't meet any fellow entrepreneur, too extreme, isn't it? ;)
I'm going to disagree with georgespencer -- not with his perfectly reasonable suggestions, but with the premise that it's not worth seeking out a mentor. On the face of it, nobody "needs" a mentor, but the entire idea behind a mentor is face-to-face networking and advice. In addition, you will be borrowing your mentor's bona fides when you're having lunch with connections you've made via your mentor, and this can go a long way. A friend of mine has Gary Reiner for a mentor -- having that kind of horsepower behind your idea is priceless.
Having said all this, your best bet is to network and seek out introductions. You can't come in "cold", but "lukewarm" is okay, as long as there's a personal connection of some kind to your mentor -- whether it's a shared vision or a shared connection.
I didn't mean to imply that in general it's not worth seeking out a mentor: I meant that for OP it's not worth it because he doesn't have anything he needs mentoring on.
If he needs mentoring on founding his startup or building a working version of his product, he's falling at the very first hurdle (beyond "having an idea"), and also the part of the process which is incredibly well documented online and elsewhere. It's formulaic.
We have two excellent NEDs at my company who are about as good as it gets, mentor-wise. But I'd never have gotten anywhere with them without first doing something.
When you're doing interesting things you will meet people who are motivated to help you.
People won't take much of an interest in a person who is looking for a mentor but not doing anything.
Stop overthinking this. Establish relationships with other entrepreneurs near you. You can shoot the shit with them when things are good and when things are bad. You'll get introduced to other interesting people.
One day maybe you'll meet the fairy godmother you seem to be seeking, but if you don't you'll have made a start and know some interesting people. And, crucially, you'll be doing something.
Edit: Just saw that you're based in London. Go to the meetups and hackathons and python dojos and LRUG etc.