£Whatever it costs you per service to do + £how much you want to be paid per hour + £if you want to pay yourself for travel time + £online calculator to work out your petrol cost average.
As for couch, tell them they need to have a place for the couch and move furniture before you get there if they have to. That it is about the size of a sofa if they aren’t sure of space needed. Doing it on a sofa will give you a bad back and in this industry we must protect our backs, so if you have to tell a white lie that you have a bad back and must use couch, tell it.
At least you can stay in one place to do those treatments so if it’s next to a bed/in a hallway/in front of their sofa with your stool at the end it’s not going to really be a problem so put it up even if space is limited.
I agree with House Beauty , such useful information. . it may help as well to look at the local competition, and charge the same as them if you aren't already.
You could factor in mileage and setting up time.
I hate mobile, do just 4 clients, always a real pain as I am so used to having all I need at home. Occasionally I have to visit them, but I do charge a little extra and never go any further than 3 miles.
Are there many salons around you that you can check prices with? Just to help give you an idea?