Jammed Stop Cock

[redden]

Hi

I am trying to fix my dripping kitchen tap mixer (cold water tap) and have referred to the advice on this site but in order to go a step further need to switch off the water. Unfortunately the stop cock below the sink will not move - have tried WD40. Don't want to resort to putting too much pressure on the pipes, therefore is there an easy way of loosening the stop cock? Alternatively will it be easier just to switch the water off at the mains - will this cause any problems elsewhere?

[thedoctor]

See the jammed and stuck water valves project