Renewed Faith in Car Mechanics

The saga of the cars continues.
Last week the windscreen washer switch on the present car went wrong. No worries, I know I have a spare in the old car, so I'll just swap them over . . . easy!
So off I go to the Haynes manual. It tells me that I have to remove part of the dashboard to gain access to the switch. It also tells me that to do that I need to remove the steering wheel. So I follow the instructions and set to work.
Remove the central cover on the steering wheel - done.
Undo the nut revealed underneath the cover . . . having finally found the right socket to fit the nut I start to undo the nut - but I can't! I use a long handle - no effect. I tap the handle with a mallet - still the frigging nut won't turn. It's almost as if it's been welded in place!
So I give up and call the local Renault dealer to arrange for them to fit a new switch.
Come Friday, they say, and it'll cost you £80. Well, we thought, it's got to be done. You can't drive long distances in shitty weather without washers.
Come Friday my wife duly takes the car in. She waits while they do the job. Then a rather sheepish fitter comes back and says that the part they ordered is the wrong one. It does the job but it is not the right shape. He will contact the spares warehouse and see if they can send the right one by tomorrow.
So today I ring them. "Have you got the replacement switch?" I ask. "They've sent the wrong one again", says Dean, apologetically. "We can try it and see if it will work but I think the shape of the stalk is wrong and may impede steering."
I commented that it was such a shame because I have the right switch in another car but cannot get the steering wheel off to gain access to it.
Back comes Dean: "You don't need to get the steering wheel off if you have the right thin T10 screwdriver to get to the screw behind the wheel. I'll lend you mine!"
I am now halfway through the job of swapping them over and just waiting for the missus to come back from shopping in the car so that I can finish the job.
I want to say a big "thank you" to Dean at Renault Minute in Staple Hill, Bristol. His loan of the tool has saved us £80 and, indirectly, I have now got a working windscreen washer.
LATER THE SAME DAY . . .
So the Missus comes home . . . I swap the switches . . . and still the bugger doesn't work! SHIT! So I try both switches in turn on the old car. Both work perfectly. SHIT AGAIN!
So I decide that it's the wiring or the connector. I fiddle with the connection to the switch. It makes no difference. I look at the connection at the pump end. Some connection, but only if I press really hard on the connector. I finally get my head under the bonnet and get the aforesaid good lady to work the switch while I fiddle with the pump. It works spasmodically. It still hasn't dawned on me that the obvious answer is the pump is buggered!
But finally, in desperation, as a last resort I swap the pump from the old car.
EUREKA!
The frigging thing works! Perfectly! Every time you press the switch!
If only I'd gone right through the whole system before taking it to the mechanics . . .