i have a tv in my bedroom at present with no aerial. i do not want to lay another line to my room, and i know there's such things as wireless av transmitters. but i need to know the best one under around £40? and i have freeview built into my tv, but the downstairs one doesn't, it gets from a dvd recorder. do i have to watch whats on the tv downstairs or can i change channels and it doesn't afect it?