London Metropolitan University is not mentioned on the INZ list of qualifications exempt from assessment.
http://www.immigration.govt.nz/opsmanual/45798.htm So it seems that yes, you will have to have your degree assessed by NZQA. Notice, they will need to assess you bachelor's degree also, to show your eligibility for points. This is the requirement for web developers on the Long Term Skills List.
Bachelor degree (Level 7) specialising in Information Technology (Computer Science, Information Systems or other Information Technology) OR Bachelor degree (Level 7) specialising in Electrical and Electronic Engineering and Technology AND a minimum of three years' relevant post-qualification work experience.
http://www.immigration.govt.nz/templ...=Guest&level=3