+1
This is somewhat dependent on the era, though. In the post-war period, there was a boom in British framebuilding that lasted until the early 1950's, when it apruptly went bust (not unlike the Amercian bicycle boom in the early 1970's). During that "heyday," most British bikes featured British components (with some French influence as well). That began to change circa the early 1960's as more imported Italian components began to be available. The more simple, Italian style lugwork became more popular among racers as well, and Campagnolo parts started to appear with some frequency. I think derailleurs and alloy cranks may have gained increased acceptance for racing/time trialing during that period as well. British component manufacture languished. The use of Italian components for racing bicycles in particular continued, obviously, more or less right through the classic/vintage period.