anyone know about the lock on the alarm siren?

[turkishdiver]

hi guys
been to the dealer today to receive the master key with remote central locking controls on.the second step would be ordering the key fob for the alarm and have it programmed.
the key they ordered started the engine and operated the central locking but only manually.remote couldnt be set.when the guy opened the bonnet there was a small round key lock on the siren which says on/off.they asked me if i got the key for it,since that was on off and i didnt have the key,i got told that they gotta change the siren which will also take about 1.5 hours.so at bmw dealer costing £140 for labour for 1.5 hours,it would come to a total of £230.
if i had that small key thing ,i would only have to order the alarm fob (£50) and have it programmed (£30).
anybody out there know where i can get a key for it or how else i can turn that on?PLEASE i will really appreciate the help.the car is a 97 reg bmw 316i se.