remove all the earths, using sand paper find bare metal and put them back on again and smear vaselin over them !!
I've just done this (except I used a mini-grinder instead of sand paper) with the battery earth strap and the engine earth that runs from the engine to the bulkhead engine mount and it's not made any difference, still just getting a loud click when pressing the start button.
Can anyone suggest a suitable place for me to attach a jump lead to the engine, so that I can earth it through jump leads to the battery, so that I can see whether it is an earth problem or not for sure before I start taking things to bits.
Thanks.