Was looking at this tariff last week and I'm sure they were only giving 4GB or possibly 5GB.
They've increased it to 8GB. The deadline for 31st October only seems to be for actually getting the offer, the increased data appears to be for length of 12 month contract. Best to double check that if it' 8GB you need.
The sweetener is the TCB of £89. It was only £53 over the weekend so that's increased too.