"Tipping is appreciated but not always appropriate in London. There are some situations where it is customary, for example in restaurants. Here are a few guidelines, although ultimately tips (or gratuities) are discretionary and depend on the quality of the service you receive.
Tipping in London's Restaurants
It is customary to leave 10-15% of the bill when eating out. However, restaurants often add on a service charge (usually 12.5%), especially if you're in a large group, so it's worth checking your bill if you don't want to tip twice. It's not customary to pay a tip for fast food, self-service or takeaway meals.
Top tip: Although restaurants (and other businesses) should make their policy clear, it's worth checking with your waiter that he/she will personally receive your tip rather than the company – particularly if you're paying by credit card.
Tipping in Bars and Pubs
People generally do not tip in pubs in London. Bartenders sometimes hand back change on a tipping tray, although it's still up to you to choose to leave a tip.
Tipping in Hotels in London
Like restaurants, most London hotel bills include a service charge, usually 10-12%. If there's no service charge added to your bill in a hotel restaurant, it's customary to tip as for any other restaurant (10-15% of the bill). For room cleaning staff, you can leave an amount of your choosing on departure. Tips for other hotel staff such as concierges and door staff are discretionary and are most commonplace for porters.
Tipping Taxi Drivers
It is polite to tip 10-15% of the taxi fare for black cabs and licensed minicabs in London. However, most people simply round up the fare to the nearest £1 and tell the driver to "keep the change". If you've had a longer journey and the driver has assisted you with luggage, you may wish to tip a little more, up to £5. "
Fonte: www.visitlondon.com
