A few points;
maintaining extinguishers- do you & your staff have a current competency certificates issued by a organisation approved by FETA, BSI, BFC or IFEDA? Unfortunately anyone can 'service' extinguishers, but without the proper training, glaring errors will be made & standards change - are you guage testing, using the Basic Service/Extended Service/Overhaul matrix, Overhauling CO2s at 10 yrs, not 20, not putting pull seals on breakable OK pins......
My pet hate is the large & small firms, from nationals to one man bands that do not do the job properly.
As you are interested in doing things right I am more than glad to help you - if you contact me direct by email I will send you operational procedures, the relevant BS extracts/codes on extinguisher provision, details of approved extinguisher service technicans courses & some good trade suppliers of extinguishers, parts & filling services
EL test keys - took me a couple of years to "find" all the different ones through site inspections - you need to sizes of fish key & a sardine tin shaped key or you will get stuck as ther eare three common types and the MK key (the larger of the two fish keys) is not as universal as it once was.
I am concerned that your employers sound like the firms who I am constantly battling against, i.e "wipe & swipe" merchants - you should be given full training - just servicing alone is a weeks residential course, exam and then a period of in house & on the job training/shadowing before anything else.