It's Europe-wide in fact. British Summer Time (+1) and Central European Summer Time (+2). Would be interested in the history behind the difference in terminology though.
I'm guessing it has something to do with a lot of people confusing which direction is the "savings" time. As in, did we just enter or leave DST? (I hear people making this mistake or its converse every year.) "Summer" time is harder to make that mistake with.
