Document revision numbering

Hi guys,

Apologies if this is covered elsewhere but a quick search didn't yield me with what I was after....

Our company is in the process of trying to become BIM2 compliant, therefore changing all of our standards over to BS1192 conventions.
I'm currently drafting up some guidelines to send round to everyone in relation to document naming but one thing I can't seem to find out is if there's an AEC uk standard for revision sequencing.
My previous company used P1, T1, C1 for preliminary, tender and construction stage drawings, my current place starts on a blank for the first issue then uses A, B, C etc to track revisions with a check box on the title block to show which stage the drawing is issued for.

Is there a generally accepted standard for this? or is it unimportant as long as it's clear and properly tracked. Whatever we opt for will have to be applicable across both Autocad (currently using mostly) and Revit (which I'm also currently learning)

Thanks.