Commercial property rent values

[vrupper]

Is there any way of finding out the possible rent that could be realised from renting a commercial property in a specific area of England? Ie any websites that give you average rates of annual rents paid per postcode.

Asking a commercial estate agent is one way but i thought there might be other ways! I have checked the government website that shows the rateable value
of properties but this is dated 1st April 2005.

Any help would be greatly appreciated.