Xbox Game Pass Ultimate Confusion

I’m really confused about the conversion of my xbox Live when taking advantage of the £1 deal for 1 month of ultimate. I understand that when purchased, I will receive a month of gamepass and i will get my xbox live upgraded to the same amount if months
I already have remaining (6 months)

What I dont understand is that if I cancel the subscription before the month is up, causing me to avoid the £10.99 a month every month after that, according to Xbox support, my xbox live cannot be transferred back, meaning I’d lose the remaining of my 6
months.

Is there any way I can purchase the month of Gamepass Ultimate for a £1 and get rid of it without being charged anymore money or losing any of my remaining xbox live?

Will turning auto renew off have any affect?

:)