The company that makes Diva showers is NewTeam, part of the Bristan Group. Details
here.
However, I searched the Say no to 0870 database for the 0870 number you provided and it reveals an entry for D
eva Tap with the number 0800 1951602. A Google search for Deva Tap reveals the company's website is
http://www.devatap.com/The 0870 number you quote is on there as being the number for sales enquiries and the 0800 number in the database turns out to be the number for customer services and technical support according to
this page which also gives
01942 687209 as the number for customer services and technical support. This number answers with a recording, the same recording that the 0870 number answers with. The 0800 does not answer at all, or at least within a couple of rings (out of hours, that is).
Another number with the same recording is 01942 680177 and is also given on the website as being a "Helpline". BT Directory Enquiries lists this number, so I presume that it is the general number for the company.
Please come back and say whether it works and take some time to read the
instructions for posting a request.