Whats the difference (apart from the obvious !) and which are better, easier to fit etc ?

Electric tend to be more expensive due to the need for a separate sensor. Mechanical will take a pipe from the source and run it to the guage - the thought of hot oil coming in to the cab for measuring is not one I am keen on! For things like that I'd go electric and for things that are of less concern, vacuum for instance then mechanical are fine

Makes sense, thanks Olly !

I took just the approach that OllyK mentioned. I really didn't want the possibility of my mistake leading to me being sprayed in hot oil :D whilst driving along.

Turbo - mechanical. Oil pressure - electric. Oil temp - electronic.

Cheers,
Nick.