Call out rate ...
its going to take you how long to get there ... its going to take you how long to get back ...
you're going to spend how long on the job ...
Do the usual calculations ... how much do you want to earn a year at this (think if it was your full time job)
(for ease say you want to earn 48K a year ... )
52 weeks in the year ... 4 weeks holidays ...
that means 48 weeks left ...
therefore you have to earn 1k a week on the job ...
a working week means 40 hours ...
1000 / 40 = hourly rate of 25 quid ...
Fixing up a printer = .. house call ...
20 minutes to get there ... 20 minutes to get back ... finding out problem with the printer .. downloaded drivers and so on (potentially) .. updating drivers and so on ... and you're looking at 2 hours work ... not to mention ... 1.5 hours parking ...
so your 50 quid rate in this case is quite appropriate ... given these figures .. maybe more
If you're making that amount then you'll have to pay VAT as well on the service you are offering ... take into consideration VAN costs (insurance / depreciation .. 20% first year and so on... fuel ) ... marketing ... lunch expenses (because you aren't at work) ... and so on. Business premises ... you may want an office ... mobile phone costs (can be damn expensive ringing people having those 10 minutes conversations at your expense) / business cards ... ads in the papers ...
Say you want to take a networking course or something ( add on 1 - 2 grand for this)
48k isn't so much anymore
Tools / equipment / (laptop for diagnoses) / multi-meters / replacement parts costs.
Unfortunately the majority of people don't think of all these things
I also realise you're doing this as a Nixer so to speak ... but think long term ...