i did hear that the mix used for anti-icing the runway,taxiways and stands was not the correct mix,instead of a 75/25 mix it was the other way round
Why on earth would they mix anything? The difference between anti-ice and de-ice is the flow rate from the rig which obviously changes the amount used. There is no water involved anywhere.
It looks like they just didn't anti-ice and were then on the back foot when it froze. Funny how the Met Office have said they don't supply Gatwick with weather warnings, so it may have been the fault of their provider, whoever that may be.