Once you apply they come round and put up the signs. They take photos of any cars that are currently parked in the bays that are being suspended.
On the day, if there's a car parked in the suspended bay you give them a ring (they're usually prowling round anyway) and they send a tow truck. If the car was one of the ones parked there when the signs went up they use the tow truck to move the car to another space, no ticket. If the car wasn't one of the ones parked there when the signs went up it gets moved and given a parking ticket.
When we last did it for moving we had to get a car moved in the morning just before the removal van came round. Bastard neighbour eventually came out and had a moan at me saying that the car has been there for weeks and they must have only put the signs up a day ago. I had the pleasure of telling him the bays were empty when the signs were put up, the council has photos of this, so go argue with them.
Of course, this is all dependent on being able to predict the day that the removals/scaffolding lorry/etc will be required.
Too late now but the usual way is to arrange a parking suspension. My local council requires ~5 working days' notice: https://www.wandsworth.gov.uk/parking/parking-bays/parking-bay-suspensions/how-we-suspend-parking-bays/
£37 per 5m space.
Once you apply they come round and put up the signs. They take photos of any cars that are currently parked in the bays that are being suspended.
On the day, if there's a car parked in the suspended bay you give them a ring (they're usually prowling round anyway) and they send a tow truck. If the car was one of the ones parked there when the signs went up they use the tow truck to move the car to another space, no ticket. If the car wasn't one of the ones parked there when the signs went up it gets moved and given a parking ticket.
When we last did it for moving we had to get a car moved in the morning just before the removal van came round. Bastard neighbour eventually came out and had a moan at me saying that the car has been there for weeks and they must have only put the signs up a day ago. I had the pleasure of telling him the bays were empty when the signs were put up, the council has photos of this, so go argue with them.
Of course, this is all dependent on being able to predict the day that the removals/scaffolding lorry/etc will be required.