Hmm, have you ever heard of 'managing expectations'?
You seem to want it all. Decent wage, decent job that isn't hard or boring and lots of free time.
It's just not very realistic. 20k is a pretty good wage for full time early on in a career, and unless you get on a grad scheme you would expect to be paid less than that.
But I noticed you are saying you don't care about the money so much. But isn't that kind of the reason you're getting a job? It's pretty difficult to support yourself on 15k a year. I'd be hesitant to put all your earning potential on a partner for two reasons:
1) It will breed resentment. I've worked full time, 9-5 + overtime for about 4 years now. It's pretty tough dragging yourself out of bed every day. There are so many other things I'd love to be doing that I'm too tired when I get home at seven o'clock. I've got books to write, that I'm reasonably good at. I've got cars to fix and a house to decorate a whole host of other things that I love doing with my spare time.
But I can't, because I need to pay for food, and energy and petrol for the car and our mortgage.
Don't get me wrong, I actually really like my job. It's what you listed, flexible, well paid. Analytical (vs creative because I like analytical). It's pretty much my dream job. But it's still really bloody hard to spend 40 hours or more doing it!
When my wife was working 8 hours a week, I found it hard. However much stuff you do around the house... you aren't really going to be dong it full time (the 'things' you wanted to do are a lot to do with yourself rather than your partner too) and it's tough working so hard so someone else gets all the nice things with none of the work. However much you love them, it introduces inequality, and that breeds resentment.
2) It's not a good idea for you to 'put all your eggs in one basket'. Your boyfriend might get fired. He might break a leg. He might get made redundant. What would you do then? A second income is invaluable for security to keep paying the rent.
What if your boyfriend leaves you? I know it doesn't seem likely now but even people who are married get divorced. In 20 years time do you want to start from rung 1 on a sensible career or already have a decent wage and experience. If you plan your life around your boyfriends income... you're taking a risk.
3) Money. Have you ever supported yourself? You never have enough money, trust me. As you get older your expenditure increases. You get mortgages, cars, kids, you live in nicer neighborhoods and buy nicer food.
Paying for it is hard. I earn a decent wage and we still struggle some months (more than when we were students). A second income is a god-send.
Do you ever want to buy a house? If so, your deposit is going to take 20 years to save up, or 2 if you have a decent second wage.
Personally, I think it's pretty selfish to want to work part time and expect someone else to provide for you. If you have to because you are working on building your own business or look after kids or just can't find a job - fine. But to just expect someone else to support your 'activities' just doesn't seem right to me. I'd hate it.