Their is no offical map of the cabinet deployment in a area as openreach do not publish this data as it is commercially sensitive.
Some people have mapped out their local exchanges via google maps and other resources.
If you use the below checker- use the number for BT numbers and the address for Sky/TT numbers, the postcode checker is less accurate as multiple cabinets can cover a postcode.
https://www.btwholesale.com/pages/static/Community/B...