I´m almost certain you could get a visa to legitimately spend the time here. Any country would be foolish not to let someone who´s going to spend a lot of money and isn´t looking to take a job from a local or use any welfare benefits. I suggest you ask at an embassy what are your options. If one isn´t helpful find another one.

Maybe enrolling into a school and not studying? If you have the means, who cares if you study or not? Maybe saying that you want to open a business and are there to explore the options? Buying a residence in a very cheap place (think "Detroit" of UK or rural areas of Northern Finland) and not staying there?