Payment as Verification
OFCOM states on their website that payment methods that require a user to be over 18 count as "Highly Effective" Age Verification.
To that end, simply pay for your Over18.uk account with a credit card and your account will be considered 'Over 18'. Website owners can check your Account ID against a list of 'verified over 18' and decide whether to let you access their website or not.
Get Started
You don't appear to have an over18.uk account (or aren't logged in), why not create a new account?