There are a few with national coverage, some employ their own fitting crews, but most are freelancers that are part of a network.
The good thing about using the likes of Midi Sign Services is that they are responsible for their men, their work etc. or it would be pointless using them because they would be nothing more than a middleman.
https://www.midasignservices.co.uk
If you go the alternative route and source and hire some freelancers, you must make sure they have insurance, ipaf, cat-scan operator blah blah. and that they will give you some sort of warranty on what has been installed, is installed correctly.
I remember about 15 years hiring two guys to install a load of free-standing sign posts in Glasgow. I turned up to see how they were getting on and i instantly questioned them on “have you dug the holes the proper depth?” I was being polite to give them a chance to explain because i knew it wasn’t. in the end, after much denial, he says “you will just have to trust me they are at the correct depth!”
I went and got a measuring tape in front of him, hooked it on the post about 4+ metres up, and dragged the tape to the ground.
“there you go, 4.5m sticking out the ground meaning that hole is no more than 500mm in the ground. you will need to remove the posts and start again!”
They had 6 poles in place by the time i turned up… 🤨 and the thing is, these guys had plenty of experience but obviously their “not the sharpest tool in the box” 😀