Possibly a bit of a odd question but, how are your batteries fitted i.e. terminals towards the engine or facing the bulkhead?

mine is the latter and I'm finding it very difficult to get anywhere near the negative terminal as it seems to be permanently loose no matter how much I try to tighten it....

On a TD6 the battery terminals are nearest the bulkhead. The negative terminal is definitely a bit intricate to fit, l tend to fit it before l clamp the battery down in position. Unclamped the battery can move quite a bit towards the engine.
If you can’t get the clamp tight are you sure it is down fully on the terminal or could it be it’s time for a new negative cable.
If the cable clamp is slack you could always do the piece of copper pipe wall down between the clamp and the terminal and then tighten trick.

My terminals are close to the bulkhead.

Towards bulkhead, 10mm pipe spanner.

I guess that it may be possible to replace the Batt with a version having the terminals LH+ve so that you could fit it the other way round?? L322 3.6 TDV8 Vogue. 07MY
ML 320 7 Seat full leather etc. (The Black Pearl)

Cheers,

As it happens I decided to make up a new earth cable yesterday as had the bits lying around so just a case of now getting the time to actually get it fitted onto the car (apparently we are doing stuff this weekend for some unknow reason so will have to rough it in a freezing cold discovery till then )