AV senders usually come in two types - one which is a small set-top box that connects to the scart socket with a lead and the other which is a tiny single complete unit that plugs directly into the scart socket. This small unit model has the advantage of not not having another set-top box. However, it does require another power outlet and an "eye" to be positioned in front of the TV or Sky box.
If the rooms are close together, especially side-by-side, you should have no problem using the small scart unit version.
The small set-top box version (which has an aerial or small dish) has the advantage in that you can position it anywhere around the TV for best transmission, so if the rooms are far appart such as opposite ends of the house, go for this type.
One thing to watch out for is that most AV senders use the 2.4GHz band, which is the same as most Wi-Fi networks and from my experience, some video senders will show flashing lines across the screen when the Wi-Fi is in use. In one case I seen, no channel choice on either the AV sender or Wi-Fi access point would eliminate the interference. So if you can, try getting an AV sender that does not use the 2.4GHz band.