Sometimes you'll see a comment about having 10 minutes to leave a parking space. This is called a "grace" period in that it was not part of the original deal e.g. you paid for 1 hour parking but you actually are allowed 1 hours and a free (grace) 10 minutes to leave.
The idea of a grace period is to stop trivial disputes about small amounts of time - but 10 minutes is the limit. We do say tickets issued for 10 minutes and a few seconds and these will be difficult to overturn so look for other lines of defence.
10 minutes rules and Codes of Practice.
If a parking company is not allowing you 10 minutes at the end, then quote their Code of Practice
The British Parking Association Code says:
The International Parking Community's Code is more vague but the accepted convention (i.e. what the courts' accept) is 10 minutes.