The colour scheme with the Union flag on the blue fins was not good due to the engine exhaust sooting it up.
Metropolitan had a milk float at Bournemouth with a 28 volt tapping for ground power. I think milk floats had 48 volt battery installations.
Channel Express had a milk float at Cardiff for the Twin Otter that did the Liverpool mail flight. For a while the pilot, (no names), used to start the right engine, then get out and disconnect the milk float ground power, then get back aboard and continue the operation. A little later he employed a lad at his own cost to do the milk float bit.
Aurigny had milk floats for baggage. One had an argument with the tail of a Trislander when it had tipped on its backside.