How much should I give if necessary? I really have no idea about it. Please light on it.
I'm only aware of the US as a country where you're required to tip. No one is going to say anything in the UK if you don't.
I read that the average tip in a restaurant is 8%.
So seriously relax. I only give tips in restaurant like most. I really dislike tipping. If I'm dissatisfied with something I'll speak to the manager, if I'm pleased I'll give thanks and recommend the place. Giving money to someone for doing a good job seems tacky to me, who am I some aristocrat giving coins to the lower class?
Sadly though it seems more common. The only place it's expected is restaurants.
Taxis: I usually round up to the nearest pound or throw in a pound or two, but tipping isn't a must-do in taxis (at least not in rural areas). In London and other larger cities, I'd assume it's normal to throw in a bit of a tip. I would also tip a taxi driver that takes me to or from Heathrow/Central London, as it is a longer journey (it costs around £90).
Restaurants: If tip is not already included in your bill, it's generally appropriate to tip anywhere around 15%, with more for exceptional service, of course.
Bars: I never tip per se in bars when I order drinks, but I'll usually tell the barman to keep the change if I pay close to the amount required, or write in an occasional tip if I pay with card. If you order a meal in a bar, it's appropriate to tip if the meal is served to you as would be done in a restaurant.
Massages/Haircuts/etc: Tipping is by no means required here, but some people still do tip. I don't usually tip for massages and spa treatments, but do for haircuts.
Tipping in the UK isn't as obligatory as it is in other places. Generally speaking, however, if you recieve "above and beyond" or otherwise exceptional service, it is nice to leave a tip.
We don't do it in England, not really. If you don't tip no one will say anything. Honest!
England is expensive enough without tipping! You really don't have to anywhere.
Actually, I do tip in a restaurant if service is not included. Around 10%. However, service is usually included so no need to tip in that case. Other than that, it's up to you - sometimes I will tip a friendly,chatty taxi driver.