Hi All,
I received my google home on Friday after taking up the offer. Been trying to set it up all weekend and after discussions with BT and Google, it appears there is an issue for iOS devices using the latest version of the iOS software (12.3.1). So basically until a fix is sorted by apple and google, you'll either have to wait or have access to an android device.
Poor show from BT not to have communicated this out to the no doubt many people who have taken up this offer.