How to deal with unfair charges

[SPLINE]

What did he diagnose?

...if you call a professional to perform a service then you have entered a contract and should expect to pay......................if the guy asks for £50 or so, I think he could force you to pay it.

I always expect to pay tradesman that I've called out, even if they tell me bad news! I would want a fuller explanation than 'You need a new boiler' though.