Tipping is not always appropriate in the UK. If you feel the service was good and you want to show your appreciation, here is a guide to customary practice:
Hotels: Most hotel bills include a service charge, usually 10-12%. Where a service charge is not included in a hotel restaurant, it is customary to give 10-15% of the restaurant bill. For rooms, you can leave an optional amount to room staff.
Restaurants: Many restaurant bills include a service charge; make sure you check the bill to avoid tipping twice. Where a service charge is not included, it is customary to leave a tip of 10-15% of the bill. Some restaurants now include a suggested tip in the bill total.
Taxis: 10-15% of the fare
Porterage & Hairdressers: Discretionary