Lots of reviewers and techie types are advising against a smart tv because you might not get all the services you bought the tv for. If the manufacturer doesn't renew the rights with iPlayer or 4OD you have lost that service. Well explained here:
http://www.howtogeek.com/176392/smart-tvs-are-stupid-why-you-dont-really-want-a-smart-tv/
If you have a decent tv already you make it smart for very little money, as explained in that review. Check out ChromeCast, Roku, Amazon Fire and all the other boxes and dongles that are on the market.
My 3 year old dvd player has all the catch up apps and youtube, I know some game consoles also provide smart services. You may have what you want already.