"So if you're a 123-Reg customer, please check your records to make sure you aren't an unwilling owner of an unwanted domain. If you are, please let us know. ®"
I'm not a customer, but I know one of my clients is - his company's domain is registered through them, with the web hosting managed by one company, and email through me. I've just looked on Nominet's WHOIS and I can see that the .uk equivalent of his .co.uk is marked as registered via 123-Reg - registered October 2017, with a renewal date of October 2024. I'll get him to check his account when I next speak to him.