Contact details should be available in WhoIs but the registrant should be allowed to opt-out . I have some names I no longer need, I'd be quite happy if people could look up in whois, find my email and offer me vast sums of money for the names... The act of opting out could be taken as an indication that the name may be registered in bad faith but Nominet don't seem to do much checking so registrants have the option of providing incorrect details anyway.
My Nominet control panel contains details of domains that were transferred to other owners many years ago but the registrant never bothered to update them so owner, phone, email and street address are all wrong, the email address is mine, the phone was disconnected 5 years ago, not sure if the building still exists.
In any case Nominet don't use any of that data apart from the email. I discovered that when someone got in touch to see if I could find out why their web site had stopped working. The client had paid the annual renewal a couple of months earlier.
It turned out the client changed email address a few months earlier. They still had the old address but didn't check the mailbox any more, hundreds of junk emails a day had rendered it useless. I logged in and did a search. I found an email from Nominet advising that the domain name would be cancelled due to incorrect information, they didn't specify what the problem was, I had to find out by trial and error.
The client hadn't changed postal address or phone number but Nominet hadn't tried to use either. The client hadn't updated their email address at Nominet . Even if the email had still been current it's stupid to rely solely on that, emails don't always reach their intended recipient, spam filters for example.
I think the problem was that the company name field held something like "Richard Cranium (trading as dickhead)" . When registering the name at e.g. 123reg (don't) there is no field for "trading as" so the client had used their initiative for greater clarity. The t/a name matched their domain name. If you log in to your Nominet account there is a separate field, for trading as, the client didn't know that. Had they provided less information omitting "trading as..." they'd have been OK.
Had Nominet followed their supposed normal process of merely suspending the name, fixing the "trading as" issue would have resolved the problem but Nominet had released the name back to the market although the client had paid their annual renewal not long before.
Rather than waste any more time trying to get any sense out of Nominet the quickest fix was to just buy the name again as leaving it on the open market any longer risked a drop-catcher grabbing it.
So Nominet do seem to wake up from time time and make a few checks but as we have come to expect of Nominet, they do it badly.
A very similar arose with a name registered some 25 years ago, it had been fine for most of that time but then a Nominet jobsworth spotted that the address fields specified the country as GB rather than UK. They threatened to repossess the name, again they didn't identify what the problem was merely that there was a problem: "the registrant details are not correct".
OK both stories date back several years and doubtless Nominet would deny everything and then claim that they've tightened up procedures anyway...