Have a look on boards.ie, there are a few threads about them. I emailed UKDirect about 3 months ago complaining about them flooding the market with all types of cars - at the time I was looking to buy an RX8 and 70% of the cars on carzone were from UKDirect. The reply insisted they have all the cars advertised in stock, but I highly doubt that, as they are advertising thousands of cars. I suspected it was a bit shabby as many of the cars had duplicate regs with different mileage and the pictures dont look real, to me anyway.
I would not buy from them anyway...