"Workmen often ask that, I always assumed it was to find out if I had a boyfriend or partner!!!!"
That'd be worse than casual sexism! Creepy! 
Those saying op over reacted etc do you not understand how smaller incidents of casual sexism lead to worse up to and including rape culture? Particularly worrying when as a lone woman you have an unknown man coming into your home, especially one who's likely to be strong and fit and easily able to overpower you! If that's their attitude to women when they're being 'friendly' and 'nice' that's worrying and should be.
Also agree I'd be dubious about his qualifications. 
AND men who behave like this are likely to do themselves out of business especially repeat business and nothing spreads faster than a negative review!
"hit them in the pocket, its just about the only thing they understand" absolutely!
"Why do the women need to grow up? Rather than the 'working class tradesman'?" Seconding this too!
I've several friends and family who are tradespeople and they wouldn't dream of behaving like this!
My most outrageous experience of this kind was when still with my ex whenever we bought a car the salesmen would try and answer the questions I'd asked by speaking to him! He'd tell them you need to tell graph " I know nothing about cars! " - he didn't even drive for the first one!
"as there are a lot of husbands out there who are a little more suited to doing minor stuff like that" good bit of internalised misogyny there too - as proven on this thread it's equally likely to be the wife/female partner who is 'a little more suited' to whatever task.
My ex was useless at anything practical couldn't hang a picture!
I however was capable of entirely setting up the house I moved into after we split which was basically bare bones, that included decorating (including plasterwork), light fittings, rewiring a couple of broken sockets, fitting curtain poles, re-fitting the back door which was poorly hung (by a supposed professional
) and wasn't shutting properly, fitting carpets and other flooring, plumbing in the washing machine etc etc ex wouldn't have had a bloody clue! My sisters the same - she had to explain to her equally impractical ex (we sure pick em!) how a garden strimmer works (when the line broke he thought the whole thing needed replaced, didn't know the line was replaceable
)
As for those posters saying they play up to such nonsense
1 I'd be bloody ashamed if I ever did anything like that especially as a mother to a dd
2 do you not consider it makes men like this worse? Potentially contributing to sexual predators thinking 'all single mums are up for it'?