Just bumping this thread as I've received an email from HealthStaffDiscounts.co.uk
The site looks fairly convincing, just seems to be impossible to find out anything about the company from the site. I thought there were minimum requirements for information about businesses trading online? Anyone with more insight on that issue?
Whois gives the same information as posted above by Nemo.
Nowhere as far as I can see do they claim any formal association with the NHS.
The impression I get - as with all of these types of sites - is that they are broadly legitimate inasmuch as you can advertise on their site, you can offer a discount to anyone registered with them, and anyone can register with them to get the discount. Whether you interpret the name and presentation of the site as implying that your details will be circulated to thousands of NHS staff is up to you.