for Hogmanay I would recomend you head north, Inverness and Drumnadrochit has fantastic Hogmanay celebrations, Inverness is a very low crime/Neds area, fireworks pipers and authentic Highland hospitality i can also reccomend the isle of Mull, i spent hogmanay in Tobermory one year and it was brilliant.

If you must go to London please be careful, it has changed so much, its a hotbed of crime/mugging/pickpockets .