I'm not so sure, there is more than a grain of truth in it. Years ago after dropping-out of uni I ended up doing building work in the UK. Finding somewhere to have a pee was all consuming a lot of the time. I think it would have been terrible for a woman! If you were working on the exterior of a house you would almost never be offered the use of a toilet. In fact often you would be locked out.
Lots of middle-class customers seemed to relish having some 'help' for a day. Seemingly normal people turned into the 'Lord of the Manor' and talked to you like dirt. I found early on as a young and naive team member that clients would come and chat to me hoping to find some information to use against the boss. I could work at someone's house for 6 months and watch them avoid me in town a couple of months later.
I once finished work at a house and saw the owner was sat at a table on his lawn with guests. I walked over to say I was leaving, and the old guy dropped his drink and ran over to me all agitated. He didn't want to talk to me with guests there!
After hours I have had 'friends' I would chat too for a few weeks in the student pubs about literature or something. I'm no Will Hunting, but... I remember one week discussing mediaeval literature with a girl (who was interested that I knew some stories from the Mabinogian, an ancient Welsh text), who then found out I was a builder and said some unkind things and never spoke to me again.
One kind gent always had a cup of tea for us at his house, and kind words about our work, but actively avoided me in the street.
It really confused some of them years later to see me in my regulation pinstripe suit, they didn't know what to say! The fact that I had been a builder was a drag on my career for a while, even with a few years of office experience people still got strange about that on my CV. One former employer told me he nearly blocked my appointment for it without meeting me, and was pleased to admit he was wrong. I don't put it on my CV any more.
So yes people can be real a-holes about manual workers. Believe it.
Tipping is not really a big thing in the UK at all, so I can't help there.