OP
RISElectrical
£100 materials might not be enough and in regards to mark up I think you are looking at it wrong, you are assuming that she can buy then for the same price as an electrician can which is wrong.
For example for B&Q have 25m of 3core 2.5 SWA for £45
I can get 25m of the same for £16 then I add my 15% mark up so you pay £18.40
So before you have considered the fact that if it is supplied by the spark you get the right thing 1st time, have a warranty in most cases and you don't have to pick it up etc you have also saved £26.60 in the process.
For example for B&Q have 25m of 3core 2.5 SWA for £45
I can get 25m of the same for £16 then I add my 15% mark up so you pay £18.40
So before you have considered the fact that if it is supplied by the spark you get the right thing 1st time, have a warranty in most cases and you don't have to pick it up etc you have also saved £26.60 in the process.