I would try and track one down if you can, though it might be tricky. The ISBN is 1-904318-07-X, good luck!
I've quickly produced a list of levers and added them to my website.
Alextrack - Lawerence Hill Junction Signal Box
I wouldn't trust the lever lead nomenclature, it's only something I jotted down and I'm a Western man at heart and struggle with Midland peculiarities. I can't believe how 'messy' the frame is, the levers are all over the place. Thank god I was born in South Devon!
A few comments that you might find interesting... None of the starting signals were "locked by the block" so they are devoid of a white band. As far as I can tell there were no electric points or signals so all the handles would be full length, levers that don't require effort to pull were cut down as a reminder. With detonator placers the chevrons pointed up for up lines and down for down lines. Levers 19, 20 and 22 worked both the point and FPL (facing point lock) so were bottom half back and top half blue.
An interesting combination could be...
29,30,37,39,42,43 (Engine from shed to say Westerleigh Yard)
24,31,32,33 (Down Train for WR)
My interest in various prototypes changes quicker then you can say "armchair modeller". Last month is was back to Newton Abbot, the past week I've been putting some more work into Midford (thankfully the Southern were responsible for the S&D signalling!). I will try to complete the details of the Midland passenger workings though, do you have a specific year you're modelling or would like to base the workings on?
I hope that helps!
Cheers,
Alex