Upgrading to BA Amex Premium Plus

[PSE100]

Hi,

I currently have the fee-free BA Amex Card having previously had the grandfathered Premium Plus card free until last year when I downgraded to avoid the charge.

My membership year is coming to an end and I’ve expenditure of about £11,800 on the card so will qualify soon for an economy only voucher. Does anyone know if I upgrade now what happens to my past spending record for the last 11 months? Will I immediately qualify for the enhance voucher or am I stuck with the much less useful economy version.

Any advice appreciated!