Yeah I think that's very important, to not just go crazy all at once. Like you said, it's about gradually acclimatising. Another factor is the importance of time of day. I've heard it said that getting morning and evening sun ("near infrared rich") helps to prepare the skin for the UV-rich sunlight in the middle of the day. There's a lot more to be said around how to do the sun exposure and how to all relates to skin damage and cancer risk.

I'm not sure about sunbeds tbh. The problem is that whereas the actual sun gives a broad spectrum of light including the invisible UV and infrared, I think artificial light sources are always limited to a narrow range. And this could cause issues for us. I actually think that we should get outside more in the winter. Last winter, I was struggling loads because (as usual) I was spending almost all the time indoors. When we started getting outside, walking, receiving the sunlight that is there, our health definitely improved. Just need to get used to the cold!