I got a more complete response from ITV:
Thank you for your email regarding the above. Unfortunately we did not produce this for DVD as we did not have the rights to do so. We believe (according to Amazon.co.uk) that 2 Entertain hold the rights to this series therefore you may like to contact them at the following:-
33 Foley Street
Tel: 020 7612 3000
Once again many thanks for taking the trouble to contact ITV and hope you continue to watch and enjoy many of our programmes.
So I then emailed 2 entertain and here is that response:
Thank you for contacting us here at 2 entertain about the availability of the above title. We are assessing the viability of releasing this title on DVD but as yet cannot confirm when it will definitely be published but it is on our ongoing schedule at the moment. Please check the BBC Shop throughout the year for further updates. We are constantly updating our catalogue of titles and really appreciate all of the feedback we receive from the viewing public.
DVD Enquiry Phone Line 020 7612 3120
Reading these boards might help them "assess the viability".
PS: I'm a lurker, and only logged in to post this. Even so, the site is great and I do visit often.