Home DIY

I have never found a huge difference for diy jobs, I currently use a 6ft long one which is magnetic, which is handy for me, as I do stuff with metal, but pointless if you are mainly dealing with wood, and has the added bonus of often losing it as I have left it stuck to a metal beam somewhere. You can get fancy digital ones, to calculate drops, but I tend to do this with a laser level rather than a spirit. Other thing to look out for is does it have an easy way to hold. But all in all I suspect the lidl ones will be fine for DIY use.

You can easily test them once you do buy them (doesn't help in the lead up, but means it's easier to trust once they do).

Set on a surface that they give a "level" result for, flip them round, if still level then they're OK. If level one way round and not the other, bin it.

Stabila are good (although their cheap ones are a bit shit).

Bmi are decent too. But if you’re not using them daily it probably doesn’t matter too much (although I’m reluctant to recommend shit levels).

I like these ones (although whoever decided to put “true pro” on them needs fired).
https://www.amazon.co.uk/Stabila-19598-True-Pro-Spirit-Level/dp/B089CWPKMG/ref=mp_s_a_1_3?dchild=1&keywords=stabila+level&qid=1604568006&sr=8-3

The best bit is that the rubber feet on either end are proud on one side so that when you hold the level against the wall, it holds in place, which makes marking lines much easier.

Having an LED light built into the spirit bubble is also super handy, as is having a peep hole on the bottom so you can see the bubble when the level is straight in front of you. Both those add to the cost tho!

Edit: this one has the LEDs but not the peep holes. I also really like having a handle on them.
https://www.amazon.co.uk/Stabila-17393-196-2-Spirit-Level/dp/B001V9XDZ8/ref=mp_s_a_1_14?dchild=1&keywords=stabila+level&qid=1604568006&sr=8-14

Spirit levels ?

As @stevo_com says, flip it over to see if it reads the same both ways. I built half a deck a few years ago with a cheap level that read differently depending on the way you laid it down. Was no fun unscrewing all the joists and starting over...