Normally between 25 to 35 pounds per circuit it will depend on many things really.
Age and condition of the installation. If it is old, in a poor condition, perhaps without any previous test results or certificates, then your sampling will be virtually 100% and all that entails then you may want to hit that 35pound a circuit quote. As in this case you will need to identify circuits and produce charts for them. I would stipulate in the quote though a time period for finding circuits, say 45 mins, and if not identified then either mark on the sheet as a limitation and why, or quote for finding them in on day work.
If it is new, or in good condition, then you can adjust the price down as there maybe full charts and certificates, and your sampling will be a lot less.
You then should factor in access and times, There maybe times that you will need to get in early or stay late, or only get acceess over night and weekend, in this case again you should be aiming at the upper end of the price range.
In your quote again stipulate remedial work. If it is quite small. ie replacing a broken socket outlet or such, then you can quote price of accessory plus 15% labour cost. If of course there are several more involved remedials then of course outline these will be quoted on a seprate job.
Emergency lighting, fire alarms or intruder alarms, should be quoted as a seperate item within your quote, or if you not doing them again make that clear on your quote.
Bottom line is what do you need to make sure all your training and expense are realised and so that you can earn a decent living.