Was going to say this. Failing that, buy online and you've got 14 days to return under Consumer Contract Regulations. Obviously the more reputable the company, the easier it'll be.
From what I've seen online, there's a few issues hitting a small minority of Switch buyers - left joycon desync, some (not that many so far as I can tell) with a couple of dead pixels and one or two that have failed outright. Doesn't feel like it's any more than you'd normally expect for a product launch - certainly not Red Ring of Death kind of issues - but it's difficult to gauge.