Just have one more thing to try before binning the Karcher which is to disconnect the lance hose and run water through the unit for a while to clear it through, been advised it could be trapped air or something blocking the stop valve, not convinced but will give it a try. Have my sights set on a Nilfisk from Screwfix so will definitely go with one of those, looks like from reading on the net they are far better for reliability than the Karchers.
Tim.
Tim.