BS 5266-1:2011 Emergency lighting – Part 1: Code of Practice for the Emergency Escape Lighting of Premises will give you more accurate guidance. However, there is no 'legal' requirement to have test key switches. Indeed, some units are self testing, so there is no need (provided they are being regularly servcied/ maintained). You don't say whether the faulty units are maintained or non-maintained units. Although a slightly higher initial outlay, we have recently switched to using LED bulkhed emergency lighting units, as there are no luminaires to replace. Also, in most instances they provide a far higher Lux level when illuminated. With regard to not replacing faulty liminaires then you could potentially be in hot water here. If they have previously been deemed necessary, and no significant changes to the layout of the workplace, etc., has taken place they would still be seen as a requirement.

Fit test switches and wire them so you can keep the main lights running when they are under test. If integral then ensure that the individual fitting can be switched (easy to do). You MUST be able to test the units (full discharge etc) so best to have switches.

Thank you all for your assistance. Nick we have a combination of maintained and non-maintained on site. No issues with replacing defective lights. I am of the opinion that we should fit test switches to allow fire wardens to carry out this function as part of their checks(trained of course). Failing that it would appear that we are expected to send the place into darkness( slight exageration) by flicking a MCB. This also goes against our own company policy that only electrically qualified persons should open a distribution cabinet/board. Thank you all again MAT