What is a reasonable hourly wage?

I recently had a gas engineer do a very small job which took him a total of 25 minutes from entering my home to leaving including providing a receipt.

As I was returning the items I had removed to allow the work to go ahead I thought about the cost of this work and came to the conclusion that based on what I was charged for the labour element the hourly rate was £156.

I then calculated that based on a 35 hour week and for 46 weeks of the year thus allowing for sick days and holidays this amounted to £251,160!

I do realise that there are overheads to take in to consideration but I still wonder was it a fair hourly rate? J. Hill