The Nafziger Works are amazing, I bought some of his material back in the late 90's & still treasure it.
W'ton Barr = Wellington Barracks, a relatively new Army establishment for this time, just a few hundred yards from Buckingham Palace - and it's remained the Foot Guards haunt up to this day.
Anyway, crucial aspect of these lists is the month - July. This would coincide with the annual Army Summer Camp, and while the facilities at the time around Aldershot Town, Aldershot Heath and Chobham Common were extensive and improving every year, there are still a lot of units listed. So that's why so many units are mentioned.