YESSS! Fantastic news. As some people have said, you had nothing to lose by going. Worst that would have happened would be they told you to leave and they cannot see you!
Some people are all 'meh, she is making other people wait longer by 'being pushy' and insisting on being seen la la la.' IGNORE.
I know 2 people who work in Orthopedic Care and funnily enough an Eye Care Department (in hospitals in my county.) They have told me that some days they have 8 people due in the morning - 8.30am appointments through to 1pm... roughly 40 minutes each. And some days they have as many as 3 or 4 out of the 8 due NOT TURNING UP. (Complete 'no-show' ... No call or message to say they're not coming.... ) Sometimes 2 together, and the staff and Specialists are all sat there twiddling their thumbs wondering if said patients are coming.
Some patients are up to an hour late! Often traffic, late buses etc, but sometimes under-estimating how long the journey takes. Sometimes a patient rings at 6pm the night before and leaves a message on the answerphone - or emails - and cancels the appointment the next day for 11am, when it's pretty much too late to get anyone to fill it.
Anyway, tl;dr, Just turning up after an appointment has been cancelled the night before, can sometimes work out, as some appointments are cancelled because of overbooking/too many patients... (And some don't turn up so they can sometimes fit you in!)
Even so yours @Cockapoosforlife was not cancelled anyway. So I'm so pleased for you! 
The 'how dare you go, you entitled shit!' posters should be apologising now. But we know they won't. 
Off topic slightly...
I was on the list for a specialist appointment in mid 2021, and was told I could wait a year. I asked to be put onto a cancellation list and said I can come anytime at a minute's notice, probably 90% of the time. 4 weeks after my referral, and 11 months before I was expecting to be seen, I got a call at 7.30pm this one Monday night, and a woman from the hospital, asked if I was able to make it the next day at 11.15am, as someone had just cancelled. But yeah, as I said, some people CBA to even let them know.
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