Thank you AV, for your advice on this - much appreciated.
It will be very helpful if you could please ask your partner for the list of documents for the Cat F...
That really makes me think that we would be better off marrying abroad and then applying for spouse visa. As you mentioned, it is still complicated after marriage?
Unfortunately, I can't give you a list of documents for Category F as it depends on your circumstances. For example, you might be a self-employed contractor...or you might co-own a limited company. The document requirements are really different. You might have dividends, or you might get your income based on contracts. You have to document that you meet the financial requirements and that you're doing so in a legal way (such as, in the case of a limited company, meeting all of the requirements of a limited company).
If you can ask a more specific question, I can try to pass that on. But it's too hard to say what you will need for category F as it has a lot of variations.
Category F is a LOT of paperwork. Because we had some complicated issues, we chose (at the recommendation of this forum) to work with a law firm. That doesn't mean it's a requirement for you (and it's not cheap), but if money is no object it's something to consider.