A service charge (tip, gratuity or whatever you would like to call it) should not be automatically foisted on a customer, surely?
If a customer feels a tip is worthy because of excellent service, then it totally at their discretion to tip and for how much. In these circumstances, I aim for around 10%. To automatically add this service charge irrespective of the service received is, in my opinion, out of order and I would expect any amount that has been added on the bill, to be deducted. When this tactic has previously happened to me, I demand that this is done.
In my experience, this method is used infrequently in the UK. If it is mentioned on the menu board outside for instance, I will take my custom elsewhere.
I am constantly amazed that in this era of social media, restaurants and cafes continue to try and pull fast ones on their customers. Word soon gets out. They have shot themselves in the foot!