Connect the console through the RF socket and tune, really should be that simple. I'm guessing that more recent TVs may only have options for tuning digital channels in which case RF won't work. If this is the case you'd be better off getting hold of a composite cable which won't require any tuning and will look better than RF. I'm not sure if RGB SCART is an option - I have a US SNES which works great with a GC RGB cable but I don't know if that's possible on a UK SNES without modification.
If you intend to use the SNES (or any other old console) regularly I'd recommend that you get a CRT, you should be able to pick one up for under a fiver. It'll look much better and you won't have the input lag of an LCD, which can be extremely noticeable when playing older games. Ever tried wall-jumping in Super Metroid on an LCD? It was difficult enough on a CRT but is virtually impossible on an LCD!