Trev
The Dumb One
A cable will deffo work. A switch is only of use if you have an Ethernet cable near the TV and want to split it (It appears not to be in your case). I would first try the TV's WiFi and if that doesn't work, temporarily use your super duper 30m Ethernet cable and then come back here to investigate the alternatives. A cheap powerline is possibility, but if you get another HDR, that will need networking for full facilities as well as the TV so possibly a powerline WiFi extender device would do the trick as well as giving you a better WiFi coverage for your phone/tablet in the lounge.