ive got one for the money you cant go wrong like said you need a number plate as it covers the one on the t4 and some pipe insulation and i just use a couple of bungee's to sercure the bikes i got mine from go outdoors £20
I've got one too, again its badged as a different make this one is a maypole. We have had it for 8/9 years and works really well. I was a bit worried about it "just clamping" on the tow ball but it takes my weight without moving at all and feeling really solid. Ours has an extra hole for a padlock which we then loop a chain through and then around the bikes. You just need some bungey straps to hold the bikes and a lighting board and your away.
I have one from a different company but looks identical and sorry to buck the trend but I would spend a few £ more and get a better one even with a bike only worth a couple of hundred I would rather feel it a bit safer on the back.