Ok, so I've just found out I've cocked up my estops.
I'd assumed the stop switch had both contact types the same, normally closed, so I've built my estops with a pair of ILDA connectors on each, running the interlock via both sets of terminals on the stop switch.
However, I've now found out that the switches have one set of each contact type - normally closed and normally open - can you see the problem??

So, is it possible to get DPST estop switches with both sets of contacts normally closed?