Also, if you are that concerned that someone else might want the name there’s no harm in buying name.co.uk, name.com, name.net, name.org and whatever else you can think of now before you start
There are some laws now in some countries (US I think) on cybersquatting, i.e. registering a name before someone else that’s already a trademark.
Regardless, check first to see if it’s already a trademark.
I spent ages trying to find a cool geeky / film reference name for a company and found all the big studios have registered just about every possible trademark from scripts even if they’re not in use. Though you can trade under a registered name if it’s clear you’re not passing off as their business, i.e. no way the two could ever be confused.
You can go for names that aren’t trademarkable, then you can’t have it but no one else can either.