Do you tip tradesmen?

[superfeathers]

My father is a builder

He's never expected a tip in his life and gives it back. But does expect to be given teas, coffees etc.

Probably why he's booked up all year round.

Well I do make sure they are well-beveraged.
For example, I have one coming up that is £1950. In my head I should be giving £2000. But £50 is £50.
I'm tempted by the above to go with the actual amount but just interested to see the general consensus.