This looks like an opportunistic seller grabbing a failed technology and trying to make a few quid quickly before everyone finds out its rubbish.
A bit like Del Boy trying to shift the Eastern European Video cameras !!
This tech was at one time considered and looked into by a few large companies ( Sony being one ) and was quickly dropped because it introduces a huge amount of artifacts. The Picture quality is terrible.
There were two wireless systems being looked at for HDMI , this one works at 5GHz and means heavy compression , leading to lots of artifacts , not the kind of thing expected over a high quality HD interface like HDMI , and has been dropped by all serious manufacturers.
The other one worked at 60Ghz , meaning no compression and a high quality picture , but at that frequency was line of sight only , break that line of sight and the signal was lost , so again , that one has been dropped by all serious manufacturers.
There is no real alternative to cables when it comes to HDMI , this maplins unit is far too expensive given its very very poor quality result.
I've got three of the Marmitek ones, branded AirSync HD (I bought them in the states). Picture quality is excellent with no drop-outs as long as you don't try to beam through 3 concrete walls and travel 60ft! 1 wall @ 30ft or 2 walls at 15ft and you can still get 1080p. They have a boost mode to allow them to send further, but only at 1080i, still perfectly good enough for a bedroom TV. I only use 2 of them, so if anyone's interested I have a boxed one for sale.