A deal breaker for what exactly?
Season tickets holders are not entitled to refunds, it's in the Ts&Cs (unless you pay the insurance). People who got tickets for the original game will be entitled to a refund on the re-arranged game because circumstances change. But then you know all this and...
It was originally called off because of the rail stike but then the strike got cancelled when Her Majesty died. The game wasn't put back on because of the uncertainty around what policing would be needed in London for events around her funeral...