Well, they changed it okay, had to do the swap myself though!Confident that I now have a fine cranked-up battery.
Bad news tho, it has not worked. I will try the earth straps next, maybe tomorrow weather permitting (no garage).
Also to to rewire the hazard lights, as they only come on with ignition. Is this a simple case of patching into a continuous live, such as the radio? Any advice or experience would be gratefully received.