You are right that a review of your FRA would be require in respect of ensuring an alternative MOE for your mobility impaired occupants. This review will need to be recorded. I would suggest it should be the aim of the temporary emergency plan to achieve evacuation to a place of safety - not a place of relative safety - in order to be compliant, as you cannot utilise the fire service within your emergency plan. In addition, I would place a clear sign adjacent, or over the firefighting lift control switch stating the lift is out of action. If absolutely necessary - eg, you have significant high risk occupancy - you may wish to inform you local fire station, but my default position for an 8 storey low risk premises would be to stick with just the sign.