Smoke detection and emergency lighting in small charity shop

Hi - I'm after some advice please... recently completed a FSRA in a small charity shop.  

3 members of staff [some elderly volunteers who are hard of hearing]. Customers = max of 10 on a very busy day!

1)  Absolutely no form of emergency escape lighting at present - not even a candle or a torch! :)  Working hours are 10am to 4pm, but i'm just worried that certain times of the year will mean the rear part of the building [both internally and externally] would be in darkness if power was lost.  I've suggested bulk head units at rear exit [internally and externally] - i'm not too worried about the front entrance / exit as it has street lighting all year round.  But is fixed emergency escape lighting over the top in this example??  Would torches be ok?

2) Open plan allows fairly good observation levels throughout.  There is an old domestic style smoke detection unit installed at the rear of the ground floor level, adjacent to the rear fire escape exit.  But they don't test it.  Whilst staff interaction and observation is high, I'm concerned that members of staff could all be at the rear of shop sorting through donations.  Or a lone worker could be working early / late and not know if a fire is occurring in the front of the shop which has no detection whatsoever.  My thought was to ask for 10 year inter-linked units to be installed at front and rear of ground floor level.  This will avoid all shadow of doubt that if a fire occurs anywhere, they will know and be able to escape.

Any advice / tips always gratefully received...I'm fairly new to this and dont want to be seen as being a jobs worth and going over the top with things!!  Pragmatic advice will go a long way...