Right so after removing grille, trim piece and headlamp I had to take all the push/pull clips out around the front bumper as far across as the inside edge of the opposite headlamp and around and under the wheel arch and take out the 2 bolts which attach the foglight to the front assembly. the one accessed on the top via the foglight cowl is defo needed to be removed, the one "under" the foglight accessed through the wheel arch liner might only have been attached to the bumper anyway - not sure.
With all this done I was able to unclip the washer block, remove the hose from the one-way valve and draw the cracked block out from the top of the front subframe assembly.
Working in reverse I put the new block in and finally clicked the new nozzle assembly into place. 2 hours work but very good to have the thing sorted :)
Matty