They do sell them here in the UK. In some cases the carton is cheaper than than buying whole eggs and separating it yourself, especially when you consider that Two Chicks liquid egg whites are made from free range chickens. When you compare that to the cost of free range whole eggs it is cheaper to buy the carton especially when they do promos or send out vouchers. Here's a list of retailers you can find them at:
http://www.twochicks.co.uk/where_comp_list.php?s=29
That being said if it's a hassle to buy them because you normally don't go to these stores than just separate the yolk. I use to use carton egg whites a lot and it made it easier, and it was a bonus because I couldn't stand yolks; however, now I love eating whole eggs.
