The reason for the recent change was that switching to the new site significantly reduced online hosting costs, unfortunately this has reduced accessibility.Veteran Cycle Club formerly had a full library of catalogs going back well before WWII that you could download for free. They recently did away with that and went to a pay-subscription model.
There is a very good book from Tony Hadland on the history of Raleigh - it's a hardcover reference book with lots of pictures and documentation. It's called "Raleigh Past and Presence". He also wrote a nice history of Sturmey Archer, but that is out of print now.
I am unaware of any published, comprehensive history of all pre-WWII British bike brands. Much of the research on these bikes, especially the lesser-known brands was done through the VCC catalog archive.
Sorry guys, I meant I'm currently out of the UK.that's a shame - I've bought a few books from Amazon.uk - often the seller will post to US even if it's not listed in Amazon here.