Re: Military Modelling articles - there are a number of errors in the illustrations, many of which have been subsequently replicated. Stamford's and Meldrum's are two that immediately come to mind. So, as with all things ECW/BCW/W3K, take with a pinch of salt.
If you can find a copy, volume 3 of the Partizan flags and standards series is better source material (bit pricey though). It replicates the BL MS (Sloane) Add 5247 illustrations, (a contemporaneous 'catalogue' of cavalry cornets, which the British Library, sadly, haven't digitised yet)
Commanders with RoF, their bases could always fly the colonel's colour (sadly, somewhat boringly, usually a plain ensign). Timmo is, of course, correct that cavalry cornets were used as personal standards rather than RoF ensigns.
The Royals fair better as they had banners - Rupert's banner, captured at Edgehill, was described as being 14 feet long. An illustration appears in the Forlorn Hope Edgehill pamphlet