Hi again, quick update. Just too knackered to reply last night when we finally got home! After an hour waiting on the hard shoulder Green flag piggy backed us to Euro Car Parts in Redhill, Surrey for the 'bargain' price of £110 where they had one belt in stock so sleeves up and then on with the journey.
We were traveling back through Belgium from the Grand Prix when the first belt and the a/c belt went, leaving us with just one belt which at the time looked in good condition obviously one belt taking the other one out. The last belt lasted for another 250 miles or so before it too let go. Ironically, with this trip being shorter than previous trips I didn't take the spare box that has a set of genuine belts!