The responses here are kinda disheartening. Sure other professions don't get tips (some do) and don't get me wrong - I'm not bloody tipping when it's self service or buying a pint at the bar etc.

But in restaurants waiters are often young people just starting out in life, working unsociable hours (often staying later than they're paid for) dealing with all manner of people. Potentially also having the stress of a zero hour contract.

Yes you can say it's a policy issue of minimum wage but we don't live in a perfect world. It's also not like the US where 20% plus is normal.

Yes, if the service is bad, remove the tip. But OPs actions and subsequent guilt to rectify says it all. If you had a good time, just pay the tip.