I've never heard of a bull shark in European waters, got anything to back that up? Porbeagle and blue sharks are the most commonly encountered larger predatory shark species off our coastline neither of which are documented man eaters, bull sharlks however are one of the most fearsome sharks in the sea and are well known for being maneaters!
However my girlfriend and i were unfortunate enough to have a close encounter with a fairly large shark off the Dorset coast in 2005. We had gone out snorkling in the bay early one morning to have a swim over the top of a rock reef about 60 meters off the shore before all the fish were pushed further out to sea by the noise of holiday makers on the beach. I have never been able to find a snorkle mask that doesnt leak so as usual was having to re adjust the mask and tip the water out of it when i spotted a black triangular shape sticking out of the water 30 or 40 meters away from us, at first it just didnt register and then all of a sudden it hit me what i was looking at, so i got the gf's attention and we both swam back to the shore, slow at first and then as fast as we could. Once we were on the beach we looked back and saw that the shark had come closer in and then watched for a good 15 minutes as it came within 15 meters of the shore swam along the shoreline for about 100 meters and then turned back out to sea. We didnt see much more than it was about 6 feet long and dark in colour with a long tail fin, after speaking to some of the local commercial fishermen and the people in the local baitshop they seemed to think it was most likely a thresher shark which are sometimes seen near fishing ports on the south coast during warmer times of the year as they follow the fishing boats in to feed on the scraps thrown over board. They also said that there are a good number of mako sharks caught in nets in the English channel every year but they rarely get reported because of the possible damage reports of 10 foot+ long sharks being around could do to the tourist trade which the sea side resorts rely on.
There is no reason for great whites to not be off our coast, they are warm blooded so the cold seas wont bother them as it would a tropical shark like the tiger shark and we have some fairly large seal populations on our northern and eastern shores, if they arent already here then it would seem the only reason they are not is because so far they havent wanted to.