Exactly… I go to restaurants only on my holiday and I tip only if I find the service worthy. For example I was in Greece and we tried 4 restaurants there and ended up going only to one cause you could really feel the difference. And even there we tipped not percentagely but as a final sum. 4 people, spent around 100£ and we tipped 10£. And the waitresses were so nice and happy, always smiling, they even hold “our” table for us later on. In other restaurants they looked at us like idiots as: really only 5£ tip…
I cant imagine paying 30£ for spending 100£ as a tip, that’s crazy.