I reckon that Halfords and other car battery suppliers who offer an installation service must keep a legion of malnourished five year olds on site to actually do the swap.
This is a new battery for a Skoda Octavia roughly in place.
Slightly above centre (and slightly out of focus) in this photo is the battery clamp and the bolt that holds it in place. Undoing it is possible with a long extension bar and a socket on the end. But don’t undo it completely otherwise who knows where the bits will end up? Once mostly undone the old battery can be wiggled out.
But how about keeping the clamp out of the way whilst the new battery is put in and then making sure the clamp is correctly orientated before doing the bolt up? I was probably still in nappies the last time one of my arms would fit down there.
Eventually I wrapped a wire around the clamp (and behind the bolt) to keep it out of the way whilst the battery was inserted, then slid the wire out (getting caught on all sorts of other stuff in the process, natch) before doing the bolt up.
I swear car designers make it this awkward on purpose.