MPSC and "The Hill"

[enfant perdus]

I watched "The Offence" the other night and it reminded me to ask about something I've wondered for years...

In "The Hill", none of the sergeants are badged as MPSC. The principal antagonists are Scots Guards and East Surreys and the sympathetic Ian Bannen is the Buffs. Looking back at some brief clips on Youtube I also noticed Royal Fusiliers and RE or RASC, but not a single MPSC badge in sight.

I know the MPSC had to expand rapidly during the war and only accepted serving soldiers, but wouldn't they have rebadged? If not, it seems an odd mistake for the production team.