Tunnie, you really were lifting my leg!
If only I lived on your planet, where this job could be completed in 30 seconds, I'd be a happy bunny.
Ok, this is how it worked:-
Firstly, I managed to pull out the level sensor, and got a waterfall, eventually got it seated and no more leaks - so far.
Next, I found the correct pump and tried to "unclip" it, but the hoses in the way wouldn't let me. I cleared a little space, gained some cuts and bruises and after much wiggling, jiggling and Anglo-Saxon epithets, removed the pump. The spigot on the pump felt gritty, so I went in search of the filter.
Torch in hand, I saw it - but no way could I get it out.
I replaced the pump and tried to wash the screen - not a drop came out.
The only water on the screen came from the sky, so I'm on a coffee break now and cleaning my cuts ready for another try when it stops piddling down....
Thirty seconds? Thirty minutes at least so far!
Ron.