so what is the labour only of say swaping a bathroom suite ?
You need to set your own prices.
Set your rate for a days work, what you need to earn allowing for vehicle, tax, fuel, tools etc etc.
Assess how many days it will take you, allow some margin for the unknown (see earlier post)
There are a lot of variables in the equation.
Who is supplying the materials ? what about flexi's, tube, fittings etc, often overlooked by customers.