Having spent several painful hours on forums and troubleshooting with Samsung support I've hit a brick wall and hoping for inspiration please!
My old wireless connection dropped out a lot so I (assuming the problem was my poor connection) got myself a whizzy wired internet connection and router installed. Internet connection is robust and fast on all devices except Samsung TV where it connects for about a minute then drops out. Samsung support say it's not the TV as there is a Mac address showing and TV connects to my network, ISP support says it's not the connection as a laptop plugged in instead of the TV works perfectly.
Forum advice I've follow already: tried both wired and wireless connections, entered manual DNS settings 8888 and 4221, software update and factory reset in various and numerous combinations. Any further advice welcomed as TV is only 3 years old and cost a small fortune.