Tipping in the United Kingdom

About 10%

If there's no service charge, around 10% for good service (guides range from 5% to 15%). Many restaurants add an optional service charge of about 12.5% instead.

Sources: [1] [2] [3]

Don't double tip

If a service charge is on the bill, you don't tip on top. An optional charge can be removed if the service was poor.

Sources: [1] [2]

No

Don't tip for drinks in a pub. Offering to buy the bartender a drink ("and one for yourself") is the local way.

Sources: [2] [3]

Round up

Not expected; rounding the fare up to the next pound is common.

Sources: [2] [3]