OK I am late to this thread - I was on a cruise.
I don't autotip - I prepay my tips. I also bring a roll of small denominations for additionall cash tips.
Now this one is for you Paul, I also tip the server when breakfast is brought to my cabin - every day.
Sure, there are Brits who moan about tipping - it is almost a national sport with some of them; I ignore them.
However there were many on my last 2 week cruise who on disembarkation said they were glad to see the back of all the tipping - and yes they were Americans - some I know were from the Big Apple.
Please, please consolidate the gratuities into the cruise fare - oh I forgot a Celebrity Sales Manager told me once that the Americans would rebel.
PS Paul - a 15% gratuity is not de rigeur in Europe; it is only generally applied to a table size of 8 or more.
Years ago in Germany, I witnessed a party of 12 friends who asked for separate bills at the end of the meal in a restaurant - go figure.