Re: I understood most of it.
When a large company that appears to be one entity at first glance turns out to be a mashup of sub-companies and system clusters, it becomes necessary to differentiate. I was attempting to poke a little bit of fun by making it seem more official than it seems to be. Perhaps I have a strange sense of humour :)
I believe RBS is actually in the process of fissioning off it's accounts in England and Wales and forming a separate bank under the name of Williams & Glyn (http://rbsbranchinformation.co.uk/). This may well account for the division in systems I described above and would likely be the actual name that takes the place of my somewhat flippant reference.