On the capacity there are various things that can reach capacity, so it may be a few weeks or could be months. So could be a whole new cabinet, or extension to existing one, another line card, more copper pair links
This will also stop you migrating for now.
In terms of what speed you can get https://www.btwholesale.com/includes/adsl/adsl.htm
and find the Address Checker link at the bottom
Type in your postcode, then select the property name/number and you will get a range of speeds that are expected.
You cannot use phone number as Sky LLU numbers don't work in the BT wholesale checker