JD Wetherspoon plc applied for the permission for change of use of the building in Corn Square, which is currently vacant.
Plans also involved refurbishment of a single storey extension at the rear, the demolition of an outbuilding and a new rear extension.
The scheme, which was refused in June this year, has been amended and now retains the basic form of the former post office sorting office.
One letter of support was received, saying the scheme would attract customers to the town centre.
Five letters of objection were received, concerned at highway safety and increased risk of night-time rowdiness and vandalism.
Conditions were imposed and members requested officers contact the applicant to seek voluntary agreement on servicing.