Can't order Fibre 900

When the higher FTTP tiers were launched back in March I had the option to order both the Fibre 500 and Fibre 900 products on the BT site. These promptly disappeared when the lockdown hit which I assumed was due to a pause on new orders due to engineer safety. The up to 74mbps products were still available. Now that things seem to be up and running again I can order up to the Fibre 300 product but the higher 2 products have vanished. I was very keen on the 900 as it was considerably less than I'm paying Zen for 300.
We're on a fairly new rural roll out and have a Huawei ONT so should be good for gigabit from that point of view. The Broadband Availability Checker is still showing up to 330 for my line. Is this a case of lack of backhaul preventing the faster speeds being available? Possibly a glitch on the BT site at launch?

Can you check another premise that you know that can get fttp on the checker and report the max fttp speed. It isn't just the olt and ont but also the backhaul capacity.

Yep, I'm assuming it it the backhaul capacity that's the issue. It's a rural location with a cluster of properties that went live just under 2 years ago. I have checked the addresses of several of my neighbours and we are all 'up to 330mbps'