Re: WHOIS was useful...
>I used to run an internet business, we would register domain names using the customer's name as "owner" but with our contact details.
I would hope that for your contact email address you used something of the form:
nominet@RC-ISP.co.uk and not Richard@RC-ISP.co.uk.
The first is clear to a human (support agent) that this is a business email address and not an individual's and thus doesn't fall under GDPR.