I just wanted to add a note of solidarity OP.
I live opposite a school and people constantly park across our drive. We have three disabled individuals in the house and there have been times when we've had to drive very quickly to hospital as a life or death emergency. I don't want to have to fanny around explaining and asking someone to move in those circumstances. Because of all of this, I get really anxious when we're blocked in.
A few weeks ago I had around 4 people park and block us in. Each time I went out and politely asked them to move. All women. All apologetic. Actually, for two of them I didn't even ask them to move, I just asked them not to park across our drive again. All very well-mannered.
Then at 7.30pm, we're blocked in again. The school is home to a dance studio where there's evening classes. Same situation - I go out and ask the driver to please not park there again because there's disabled people in the house and urgent access is sometimes required.
Except this time it's a bloke. He was confrontational, aggressive, and told me he could park wherever he wanted to. He told me I'd come out "with an attitude" - I hadn't, but I had politely asked him not to park there again - I mean, heaven forbid an actual female tries to assert a reasonable boundary.
He then tells me that not only can he park across my dropped kerb, he can even park ON my drive if he wants and there's nothing I can do to stop him. He told me that several times.
I stood my ground and gave him as good as I got but I was physically shaking when I walked in (I'm autistic and hate confrontation!!).
He was obnoxious, sneery, and aggressive from the start.
He was only quite a small bloke - I should have sent my DP out to ask him. He's an absolute mammoth of a man, I doubt the little gobshite would have copped the same shitty attitude with him!
I would never block someone in. Absolute entitlement of it.
I would definitely park across your own drive OP. That will mean that dickhead builder has to find somewhere else to park. He can block his own customer in. Fair play to you for standing your ground.