Generally British people like trainers, jeans, sportwear and logos. We might not like clashing colours but we end up wearing them because that's what our shops sell. We have clothes that are specifically intended to be worn on holiday and sometimes hurt your eyes in strong sunshine.
British men have shorter hair than the average European man unless he's on national service, just out of prison or is a neo Nazi. Women tend not to bother with hair and make-up during the day.
We carry WH Smiths bags we got at the airport with our newspapers until they break. Then we replace them with flimsy ones from local supermarkets.
If we have a bag we bought for itself rather than the item that came in it it's a black, nylon rucksack.
We tend to overdo the sun and inappropriate clothing while walking around town because we don't get much sunshine here.
Italian standards of grooming and selection of clothes are definitely better but can be a bit dull. The women wear more jewellery. Most men have haircuts long enough to require the purchase of a comb.
Italians grow up learning how to put things together. Style-consciousness hits us from about 14. Therefore more young Italians look middle-aged and there is no such thing as the Italian goth (generally).
Italians of both sexes receive a navy Husky jacket on their 35th birthday. Men love pastel cashmere that they wear draped around their shoulders at home and shiver in here.
The 'English' look is popular with Italian men - brogues (often in tans that only work in southern light), tweed jackets, check shirts - basically not English at all.
Italians have more footwear that you can't wear to play sport than we do. The women spend a lot more on beachwear and accessories. Bikinis veer towards the Nancy Del'Olio look - padded cups and gilt trims. Italian women do not go topless. If British women spent that much on a bikini we'd probably wear both bits too.
Italians move in groups. They stop dead in groups too. Teenagers, but many older people who should know better, clutter up doorways dithering over the menu when northern Europeans are trying to get to the bar.
Italians don't drink nearly as much as British, Germans, Dutch and Scandinavians. They are generally fussier. Consequently big groups of Italians aren't as welcome as you might think in restaurants.
Haven't really made a detailed study of other nationalities beyond the observation that Germans, Dutch and Scandinavians tend to be tall and Eastern European women favour hair dyes in colours that are not found in Nature.