Ah
Now it all becomes clear. Then yes i would go down the route of an AV sender, not having one myself i cant recommend a brand, but what i will say as i have dealt with them, what you pay for is what you get.
And remember most of these will only have a scart input. Sorry if i'm telling you how to suck eggs here. So some conversion may be required...
I would recommend going to argos because if the one you buy is rubbish, you can return in and get a refund saying it is poor, same with all major high street shops as they have a 14 day technology guarantee, where if its rubbish you can return it.
With regards to WI-FI interference, they do work on the 2.4GHZ range, and have a range of approx 30m but i'm unsure of the channels, i doubt that they will be the same as WIFI, but you can always change your channel on your router if there is a problem.
I hope this helps...