Resubscribing to Xbox Game Pass Ultimate and Conversion of Live Gold

Just before Xmas 2019 I received an offer of Xbox Game Pass Ultimate for £1. I had ran out of my gold subscription and I thought this was a good deal and decided to accept it.

I cancelled it just after it came to an end as I didn't want to pay £10.99 per month. Later on I realised that if I had stacked my account with Xbox Live Gold up to a maximum of 36 months I would have had all my gold time converted to ultimate. I was kicking
myself.

I then recieved an email today from Xbox asking if I would like to get ultimate for £1 again. I click the link and then it only offers it for £10.99. No matter what I do I cannot get ultimate for £1 again even though I have an email to say otherwise. I am
guessing it's because I had it before.

My questions are these:

1) Is there a way to stack my account again to take advantage of getting ultimate at the lowest cost? i.e. If I stack my account with live and then buy a 6 month ultimate card?

2) If I do the above will it convert at a 1:1 ratio or will I lose live months during the conversion?

3) Is there another way to get the most months of ultimate at the lowest cost I have not thought of? Why would Xbox send out the promotion if it isn't valid?

Any help on this would be appreciated.

:)