Sub-Roman Britain (Cavalry etc)

[Medicus matt]

Medicus,

the literal translation is; and this will sound incomplete "The Horsemen of Aurelius' Shieldmaker" or "The Horsemen of Aurelius Shieldmaker". Also, I can't think of another member of a patrician family with that name in Britain at the time. (The idea of Patrician is infered from Gildas' staement that his parents "Wore the Purple".)

It doesn't mean shield maker, it just means 'shieldmen'. Aurelius' mounted shieldmen. The use of 'Aurelius' in that title doesn't mean that they belonged to anyone called Aurelius, it might be an indication that the unit was raised by instruction of an Aurelius (after all, the II Augusta didn't belong to Augustus) or it might be an honorific granted to the unit for having fought well.
I wouldn't get too hung up on the use of 'Scutarii' either. It was a common enough title (along with stablesiani, promoti etc) for vexillatio comitatensii which might have referred to a specific role or attribute at one time (eg they acted as 'shields' on the flanks or were bodyguards etc). I think the most you can take from their name by the time the ND was compiled is that they might once have been the elite mounted bodyguard with some connection to an Aurelius.

More importantly (being the bit that you seem to be the most blinkered about), why do you think that any mention of 'Aurelius' has to be associated with Ambrosius? It was the nomen of many noble romans (including Emperors) for hundreds of years before he came on the scene and it wouldn't be unreasonable to imagine that the Scutarii had been raised by or were named in honour of someone completely unconnected with Ambrosius. The emperor Aurelian ended up with the family name Aurelius because his father was a tenant of a senator of the same name. Huge numbers of

If you cast your research a bit wider, rather than just fixating on Ambrosius, you'll find evidence that the Equites Scutarii Aureliaci were stationed at Zeugma in Turkey sometime between the late second and early fourth century, prior to the composition of the ND (where, probably entirely coincidentally, another Aurelianus was consul in c.400 AD).
As for their origins, one paper by Speidel makes a case for them having been raised in Gaul, another theory goes that they were part of a cavalry unit of Moors.

Sorry AotB, I know you're putting a lot of research into this but it's too narrowly focused. You're limiting yourself to finding things that fit your into your desired outcome without then doing what academic research demands, which is that, once you've found something that might support your theory, you challenge it to see if it can be ruled out as supporting evidence.