This is so common in building works and its horrible to be on the receiving end - once a rip out has been done, it puts the 'extra' into blackmailing territory, because the conversation goes "I'm terribly sorry, but we've underpriced, we can pull out now and leave you with a mess and having to wait for somebody else or pay more to us"
Was it a genuine mistake on their behalf?
My guess is block driveways are about £80 to £100 a sq metre from memory, so you should be able to get a ballpark idea.
I would say it was a non genuine mistake but me and Amanda were at work, kids at home and guys paused on site with a mountain of spoil. I had a row with the boss, got to £500 then felt angry that I’d been soft.
It’s close to 100mtrs and we paid £8000 up from £7500. We were also quoted £5000 and £9000 but 2 others.
I thought it would cost close to 4 in materials so gave the £5000 guy a swerve, the guy we chose at £7500 we had seen his previous work and got his number that way.