Do you happen to know the typical speed to be expected from a newly enabled exchange? I'm expecting it will be limited to bt infinity packages, hoping the 76mb package is available but even the lowest would be better than the typical 8mbps we get now.
Service with a sync speed of up to 80/20 is available from the cabinet being enabled. The actual speed possible on your line depends on various factors, with cable length from the cabinet being the most significant factor.
Openreach offer service to all CPs from the cabinet being enabled, but those using non-BT Wholesale backhaul (notably including TalkTalk and Sky) can take some time to sort out connection between Openreach's equipment at the handover point and their own networks.
You do not get any sort of priority by ordering BT Retail's Infinity.