Just found this on NTLs site :
Is this upgrade available to existing ntl Broadband customers?
Yes. All existing 150K 600K and 1Mb customers will be included in the upgrade.
The rollout of the service enhancement will take a few months to complete as ntl need to carry out network upgrades to ensure that all of our customers continue to receive a high quality of service.
If you are a 1Mb Set top box customer ntl will be in contact with you to exchange your current box so that you can receive your 1.5Mb upgrade.
Due to technical compatibility issues you will require a new set top box in order to take advantage of the 1.5Mb service.
According to the postcode checker she should be on the faster speed at some point during august