I'm buying a new car battery since the 'current' one had dropped to 11.4 volts, and (unsurprisingly) wouldn't start the (2 litre diesel) car[1].
Most on-line places have a car registration look-up 'app' which identifies parts suitable for your car. On all the web sites I tried the 'app' looked identical.
I used the app Tayna Batteries and that showed me batteries which were suitable for my car.
I used the app on Halfords (I was feeling lazy and considered NOT DIY-ing) where they showed me batteries which at first sight seemed OK, but the terminal locations were reversed and hence were very much not OK for my car.
I'm not sure how this can happen since the car registration apps look identical on both sites.
(I've ordered a Yuasa battery from Tayna and will DIY.)
[1] I did get it started with my Noco jump starter, but this battery will let me down again at some point, and is overdue for replacement.