Hi --- You could ring the finance company number shown on the finance agreement first thing Monday morning to see if the credit has been counter signed and accepted, if not tell them you do not want it and not to sign, you must then confirm this immediately in writing by Special delivery..........but if you have had the keys for two days then the finance will most likely already have been accepted and processed, there is very little you could do to cancel this agreement unless it does not conform to the legal requirements.
You would need to take the agreement to the CAB to see if the above applies, if not then the car is yours I'm afraid. However the other concerns you could ask them to rectify, but don't hold your breath about them putting those things right. !