This applies to me-
My income is enough to apply for the Amex Platinum card but I first started out with the Amex Green Charge Card and the Amex Blue Card. I just upgraded from the Amex Green to Amex Platinum.
Here in the US, the Amex Platinum income requirement is waved if you have another Amex card for at least 6 months.
I'm not sure if this is the same with UK applicants.