When I was on the tools I use to charge £60 for the first hour and £30 for every hour after that for call outs at unsociable hours. I never had a problem with a customer paying either and I remember being at a couple of jobs for 10 mins sometimes, but every other customer did have an Austin Martin in the drive. I just made sure it was clear over the phone before I left and a lot of these call outs seemed to be on a Friday and Saturday night, I also think it depends on alot of what areas/customers you served. If I got to the house and there was a little old lady there, the call out fee would change to a cup of tea and a biscuit.
I'm sure some would disagree what I did, but this was an average cost around my area and some Sparkies and plumbers were much more expensive. You could always do a little research and do a couple of cold calls, I'm sure I have even seen some sparkies advertise it on the webpage etc, its not very nice idea but its business, just make sure the Sparky you cold call isn't a forum member
. The way I see it is call outs that happened during awkward times took me away from time with my family and a comfy warm sofa.
I got a local appliance engineer to come and fix my washing machine once, after I had spent hours taking it apart and trying to solve the error message myself. He came and tilted the washing machine by accident to get to the back which I had already done, but I think he must of tilted it a little further than me and that cleared some water from some part of it and praise the lord it cleared the error message, this took 10 mins and he charge me £50, I was a little peeved that I didn't tilt it a little more lol, but I paid up because I accepted the charge before hand and this wasn't even a call out, it was an arranged appointment.
Just remember "what you have are a very particular set of skills"