Anyone have experience of using the Platinum room availability guarantee when all the hotels in a city appear full?

I have used the guarantee for the first time to secure a booking for the 3rd June in Coventry to attend a concert in the Ricoh Arena.

All the Accor hotels in Coventry and out as far as Birmingham are showing as full (except for Platinum guaranteed availability rates) as appear all the other hotel brands within the same radius.

I have booked the Novotel Coventry M6 as it's the closest hotel to the concert venue paying nearly double the rate I would normally expect to pay for this hotel but there is nothing else available (unless I use the guarantee) and walking distance to the venue is important.

Having made the reservation using the avaialbility guarantee what are the chances of being walked especially as all the other hotels in the vicinity are full that night also?

Out of interest how does Accor make the guarantee work? Is a percentage of rooms held back for this purpose?

If the hotel does need to walk guests how will they decide who gets walked?