So got a new battery to replace the knackered one - gone to replace and THE STUPID HARNESS SCREWS ARE STUCK. Have WD40'd them but no joy yet. Any suggestions?
If they are rusted badly, it may take a while for wd40 to get working. Also, I'd be worried if you have water getting in to the battery area to make it rust.
How about tapping the screw with a hammer to see if the shock may loosen the rust in the thread ? And try to tighten the screw to break the hold. I presume you've tried a socket instead of a screwdriver ?