Agreed, very much a London thing. Given it's optional at least you can tell them (or a manager) in the UK to take off if service is crap. In Asia, in places where the service charge is added then the service charge is rarely if ever removed, you can be screaming blue at them due to a chain inexcusable lazy fuck ups and they still wont budge on the service charge - loss of face, lack staff empowerment, 'till say no' etc...
The addition of sales tax and service charge is more a frustration than tipping to me, tis why I hate restaurants in Asia that are ++ (10% SC + 7% tax). I'd like to ask them a) under what circumstances do I not have to pay the tax? b) if service is crap are you going to remove the service charge, the answer basically point to everyone pays it. I prefer wysiwyg pricing and tipping for the real extra mile. Also note service charge is rarely distributed fairly to staff that are serving you.
Definitely something I've noticed more in London, though I sometimes see "Suggested gratuity: <amount/percentage>" outside of London (generally not included in the price by default). Incidentally, suggesting a tip (especially including it in the amount by default) makes me much less likely to want to pay one.
