It all depends on how open you are as an adult model or do you need discretion? Are you looking to generate new fans/business via your website?
Choosing a domain name
Always go with .com, use word/s relevant to your niche/service or your performer name, no hyphens, keep it short, easy to pronounce, brandable.
If you have a really relevant keyword but the domain .com is already taken then .co.uk or .net
Only directing existing contacts to your website, then .co.uk, .me, or any other domain extension is fine and the name itself not as important, as long as it has some relevance to you so your contacts get a feel it's actually you and safe to use.
Where to buy a domain from?
I use 123-reg.
There are others but I have experienced issues with godaddy and namecheap before.
What to consider when registering your domain?
The registrant details.
What contact information you enter as the owner of the domain may need to be verified by the registrar at any time, some of which is publicly available on the whois database. I use a variant of my real name, a mailbox address, a dedicated email address and phone number of my spare sim.
Registering as an individual limits the amount of information published publicly and registering as a company will limit the amount of personal information you have to provide but this can also be obtained via the companies register which will have the company owners real information.