How are they getting in? Surely the Police or your security company can pinpoint week areas?
I dont know teh layout of the shop...but...surely there must be a way securing it?
You should try and get some way to track these individuals or teh equipment.
I have used a widely available service, to track down my wifes Ex when he has teh kids. Didnt know where he lived (sounds irresponsible I know, but tell teh courts that!)...we got a small mobile phone...registered it with a company...then once taht was set up... you can track that phones location to with a small area.
Its designed for parents to monitor their childs location, to their mobile phone...we bought the service in BHS of all places.
If you get a small enough phone, you could shell it, and fit it into teh grips of a gun...etc...im sure Jack could sort something out, he's a genius.
If you put it in a decent gun, it is sure to be taken if they come back...then you can track it as soon as you are made aware of teh burgalry.
http://www.childlocate.co.uk/
Ok...its not exactly pinpoint accuracy...but...with several attempts ina given period, you could work out something..especially a vehicle during teh early hours...i assume they use a vehicle?
And then pass this info to teh police....
Have you thought about Dye packs...and not of the Core variety?