I thought there was a guide, but I can't find it.
If facelift:
Open bonnet.
Unplug washer pump electrically (washer pump is the smaller of the 2 pumps on cars with headlight washers), by pullying up rubber cover over pump to access connector.
Push top of pump towards back of car, it will go with a noticible click.
Lift pump out and rearward (about a 30 degree angle) to withdraw, but you'll have to disconnect 1 (saloon) or 2 (estate) pipes before fully withdrawing.
Lots of water will escape at this point, if the washer reservoir is full.
Remove rubber grommet that will still be in the washer bottle, that provides the seal between base of pump and bottle. Probably lots more water will come out if this is blocked.
Clean the filter/gauze that is integral to this grommet. Will take a while. I find a small brush (toothbrush) and a pin/needle the tools for this. Don't be too rough with it.
If there was a lot of white slime/gunge, flush the bottle through as best you can, and start using more screenwash in the future!!!
Refit grommet, ensuring perfectly in place.
Reconnect hose(s) to pump and refit pump by lowering at the same 30 degree angle, press in place fully, then clip it forward/upright.
Reconnect plug, put rubber cover back on pump.
Enjoy a cup of tea, smug in the knowledge you've done it.
Prefacelift:
As above, BUT diconnect battery (as fans aren't guarded and can start at any time, esp with water being splashed everywhere), and remove the grill.
PS: take some pics, and send them to me, I'll do a guide (unless you want to write one

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