They are tops!
I have a couple of the Kogan tellies, plus one of their vacuum cleaners, and for their price (Australia is generally more expensive for equipment than a lot of other countries), you get a lot for the money.
The quality of the build on the units is top notch, customer service is good, price is good, and in a lot of cases they improve on things pretty well.
For instance, one of my Kogan LCD's (32 inch) uses an LG panel, but (thankfully!) does away with LG's absolutely hideous control interface, and replaces it with Kogans own design, which is much better.
If the price point works for you, they are definitely worth a try.
Here's hoping this plucky Aussie can make it in the UK! Competition FTW! :)