Apple are not here, we are fellow users here on these forums. What country are you in ? This page lists what content types can be re-download where : http://support.apple.com/kb/HT5085.
Even in countries where TV programmes can be re-downloaded, like all other content, there is no guarantee that they will remain in the store for re-downloading in the future (TV companies, and other content providers, occasionally remove their items from the store). If you haven't got copies of them on your backup of your downloads and if they are still in the store then you can try contacting iTunes Support and see if they will grant you a re-download : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption