The Information Commissioner's Office issues the following instructions: -
"If the email addresses or mobile numbers in question are those of individual subscribers, the third party will not be able to use them to send unsolicited marketing material unless the subscriber has consented to receiving it from that third party (that is, ‘the sender’). You must make clear who you are proposing to pass the details to and what sort of products and services they will be offering.
For example, a positive response to a question such as ‘We would like to pass your details to specially selected third parties so they can send you more information about holidays in America. Do you agree to this?’ is likely to be enough to allow third parties to use those contact details for promoting holidays in America by electronic mail.
A phrase such as ‘We will pass your details to third parties unless you write to us and tell us you don’t agree’ will not be enough. You should not use contact lists that have been obtained like this.
Only the individual should decide what happens to their electronic contact details. You must not disclose an individual’s contact details to third parties for their marketing purposes unless that individual actively consents to this."
This means that if you want to go down this route, you need to make it very clear to the individual who is signing up to receive communications from yourselves, that their information will be passed on to very specific companies offering the following services, etc and those services need to be very clear also.
As a company, we would advise against passing on individual's information to 3rd party companies