my car has been covered in cement dust by neighbours builders

[remnant]

my car has been covered in cement dust by neighbour's builders
i took it for a standard hand wash yesterday and it didn't come off
the guys said that if i took it in and left it with them for a few hours they could get it off

neighbour's builder says he will cover cost (£50) but I've never had a car before and I wonder if I'm missing something.

will the paint work have been permanently damaged? Is there anything else I should be doing?

thanks

A quick search suggests undiluted white vinegar: spray it on, leave it a few minutes, repeat the spray if necessary to soften it up further, then a high pressure washer to rinse it off.

Or, if they're going to pay for it to be done by someone professional who knows what they're doing, take it there and take the money.

thanks wmittens
didn't think to google it