.../// the time I got there the driver was not there (it was his last day apparently, don't know if that was due to the accident) but his colleague accepted full liability and exchanged details. Called him yesterday and he said his fleet manager filled and submitted a claim form.///...
These circumstances may well prove to be the complicating factor in view of the absence of the driver alleged to have caused the damage, a third party (not being the driver) accepting responsibility for it and the suggestion that the matter has been reported to the 'Fleet Manager'.
There are too many loose ends here as far as I would be concerned to be confident that this was going to be a straightforward matter to have resolved in the absence of much ballicking about.
I would re-visit the scene, take photographs of where your car was situated and of the relative position to the entrance of the premises concerned, make a fully detailed accident report to your own insurance company giving the name of the person accepting responsibility for the damage caused and ask them for their views.
Thinking about it, how any person can accept responsibility for the actions of others - especially where damage has been caused in circumstances where traffic offences may have been committed by the driver of the vehicle - may well depend on obtaining a full statement of facts from that third party for this to afford any traction whatever.
At best this third party is a witness to the incident unless he/she played an active part in its development - such as guiding the driver of the car around an obstruction or actively doing something to cause the driver to lose control of the vehicle resulting in the circumstances we see here.
In the circumstances - providing there is no possibility of self-incrimination - a report to the local Peelers may also be of help.