Do you mean you contacted someone about your problem, then fixed it yourself, and THEN heard back from the repairer?
If so - I guess £50 is fairly high, but sometimes when I do repairs I still charge for 'bench time' even if the problem isn't something fixable by me at that time.
For example, if someone drops in a bass with active circuitry and I spend a good while with it, I can pinpoint perhaps exactly where on the circuit board of the pre the problem is, but won't fix it, because im not a circuit board repairer type blokey. I still ask for some money for my time though.
Unless it was someone who wasn't a moron, in which case I'd probably do it for free. (Not saying you are a moron, but 90% of the people who get me to set up their guitars etc. are fairly irritating).