Fairly easy fix mate...
You need to remove some of the cowling from around the drivers side of the windscreen (sounds worse than it really is) and then work your way back from the wipers, and find the tubes which supply the water.
You may need to unhook them from underneath the cowling, along the bottom of the windscreen.
There is like a Y join in the pipes at some point, which is a non-return valve. This is known to get clogged up from time to time, so pull the tubes apart at this point and try to clean it.
Keep giving your washers a blast and you should see the water coming through easier once you've unblocked it.
Probably about 30mins total work pal.