@Okaydan The email should follow soon after the installation and I'm sorry you haven't received it yet.
You should be able to claim your Gamepass by logging into MyBT with your BT ID and password, once logged in click Manage on Your Products then scroll down to Content Partners and Add now under the Xbox game pass. I have seen this taking a couple of days before it's available to be claimed after your service was upgraded.
Thanks Neil! Absolute legend!
Yeah, was confused as it only said one month.. But read the fine print and it said BT would know the exact amount of months and it all went perfect.
Thanks again @NeilO
@Okaydan Nice 1, yeah the subscription is provided one month at a time for the duration of the offer.