Similar have been posted before but I hope this title helps people to find it. 

Washers packed up after a heavy frost. Checked Fuse46 which seemed like the right one, labelled 'Front and rear window washer'. It was ok. Checked voltage at the pump by pressing switch. Voltage was about 10volts but dropping to about 4. 

Assumed if voltage there ( I'm no electrician) then pump must be u/s. Not so. Replacement of pump made no difference.

Read forum and directed to Fuse22, labelled 'Front and rear windscreen wiper system' . Fuse was blown. System worked ok again after replacing Fuse22. 

So check this first. Hope this helps someone.

Big thanks for this, the manual doesnt really help it when the mention of washer is on another fuse,