Stations do not have peak and off peak times, rather time restrictions depend on the ticket held. Each restriction is given a two letter code which can be looked up on National Rail Enquires.
To do this find the restriction code that relates to your journey. If you already have the tickets you can find them in the following places (highlighted in red):
In this case the new format ticket has a restriction code of WZ while the old format ticket has a code of 1C. To look these up on National Rail Enquires you would go to nre.co.uk/WZ and nre.co.uk/1C.
In this example a restriction code of 1C means for outward travel
Not valid on trains timed to arrive in London Liverpool Street or London Kings Cross after 04:29 and before 10:00.