If you would like to contact Mark you can try any or all of the following methods:
Email: mwclarkson [at] gmail [dot] com (apologies for not including a mailto: hyperlink but I’m not a huge fan of spam).
Twitter: Look for @mwclarkson
Delicious: Look for mrclarkson this time (not exactly consistent, I know)
Newsgroups: If you have the time, the inclination and the know-how then please join in the discussions on uk.education.teachers and uk.education.schools-it.
Forums: Please also feel free to join in the discussion at the TES forums (http://www.tes.co.uk/staffroom/ICT)