Howdy! If your first brisket seems to be dry and tough/hard, it most probably wasn't cooked long enough. Briskets cook in a counter-intuitive manner to what one would expect with most meats. They will be dry and hard when the temps are around 160-190ish°F, and then get soft and juicy as the temps climb, sometimes on up to, and even over, 110°F. On the other hand, it is my understanding that everything is usually quite overcooked in England, so you might be just fine.......:)
Good luck with it!!