I don't get call-outs, but I know in my area it's £150, to include 30 minutes on site. I know this because a friend called me on a Sunday afternoon in a panic because dinner was in the oven and friends were due...and her kitchen lost all power. She called a local electrician and the above charge was what she was quoted, however he couldn't come to her house for at least 6 hours. She panicked and called me...
I talked her through the usual stuff, what breaker tripped etc. Long story short, the faulty circuit was identified in the usual way (RCD tripped, switch off MCBs, reset and so on). The culprit was the garage circuit which also ran the outside lights, 2 of which were full of water, and it had been pouring with rain for 24 hours. 10 minutes on the phone and the leg of lamb was back on track.
She turned up at my door 3 days later with a case of Rioja instead of a call-out charge-perfect!