There's actually loads of pre-1850 buildings in Glasgow. Here's a few well known ones....
The original tower of the Merchant's Hall (long since demolished) still stands proudly over the Briggait. This tower is from 1659.
The Virginia Buildings in Virginia Street date from 1817. That's the building that has the shop Jacobean Corsetry. No photo I'm afraid.
St George's Church is from 1807.
Carlton Place is from 1802.
The former Royal Scottish Automobile Club building in Blythswood Square is from 1823.
The old Royal Bank Of Scotland building that is now home to Borders Books was built in 1827.
The Custom House in Clyde Street dates from 1840.
The Western Club building in Buchanan Street is from 1841.
The Argyle Arcade is from 1827.