This is a fantastic site with more recorder eye candy than you could shake a stick at!
I was sure that I'd posted a link to it but I guess not.
Anyway, if you're looking for info about that EMI BTR 1 or a Boosey and Hawkes wire recorder, this is the place.
They also have a forum where rare schematics or these rare machines are shared.
Be sure and check out the "Machines Wanted" section for pictures of some super rare machines.
Also, don't miss the description of the site owners "Tonschreiber" found in the gallery.
http://www.vintagerecorders.co.uk/Oh, when I get around to visiting the UK, this guys on my list of must visits!