Actually, some of the suggestions were very helpful.
I know what I'm going to do, and this thread made a huge difference. 
So, thank you BLF for helping me in this decision!
Hm? Why would I get worked up either way? I’m not the one taking it personally.
Well, yah, that’s pretty apparent. :laughing:
To be fair, the ability to create good analogies is a gift, and not many people seem to have that gift, in my opinion.
For example, I usually cannot come up with good analogies, so I usually don't make them. 
I claimed ‘goods not as described’ through eBay and the seller gave me the partial refund that I asked for.
I did bluff a little, but I did not lie (which is important to me) and assuming nothing goes wrong anytime soon, I will give the seller positive feedback.
Thanks again for the great advice that I received!
I really didn't think it would work, but I guess I got lucky.
You put a curse on me you pesky Raccoon! 
Today the kids Nintendo switch started to do the controller ‘drifting’ 
It seems to be just the left one, my daughter managed to recalibrate the other and it seems to be ok, for now - I think I’d rather send both back though, because they were both doing it. Do you think I should bluff and say they booth are faulty - or tell the whole truth, nothing but the truth? (ie one is actually nerfed)
After reading up on it, looks like it is a common fault and should be fixed for free/exchanged.
Apparently they even do it out of warranty, luckily this had a 2 year warranty (I think) and give you another year warranty from there.
I bought it from Currys /PcWorld but via ebay. I think that counts for the 2 years. I never thought it was a very good design, wobbling around as the joycons do.
I'm not sure what you should do about telling the truth or not.
That's for you to decide.
...
Are the controllers made by Nintendo?
If not, I would replace them with official Nintendo controllers, if possible.
I honestly don't know much about the Nintendo Switch, but I do know that third party controllers usually aren't that great.
I'm actually still surprised that the fake "Sony" PS3 controllers are actually pretty good.
Yeah they are original Nintendo ones, I think I’ll just email them rather than filing a repair just yet - see what they say.
I’m not a liar as such, they both did mess up but one seems to have been able to recalibrate - I guess one side gets used way more than the other, having not really played it I’m not that clued up on it lol!
I read you get your 1 year warranty renewed anyway - so either way it should come out ok even if the other went wrong later……
Bit poor for a £300 item that is 3 weeks over 1 year old - it’s not like it’s even played a lot really. My kids are along way from hardcore 12 hr a day gamers, more like an hour a day.
I would message them first, and if that doesn't work, follow this link if you used ebay.co.uk:
Thanks 
, I’ll update with what happens……