Late charge £10 for 15 mins late first time

[MyMorningHasBroken]

I'm a bit peeved. I have never been late to pick up my youngest from nursery (he is in pretty much full time as I started work again not long ago) In fact i pick him up as soon as I can which in general is about 3/4 of an hour earlier. (obviously I have to pay the whole session). I've never been late with payments ect.
Anyway, this week, I had a flat tyre which needed changing on my way home from work. I called the school (nursery is ajoined to school) to tell them I might be late and what had happened.
They said 'oh yes, don't worry, that's fine with no mention of any fees ect, but just received my bill to find a £10 late charge. I was about 15 mins late in all.

I understand that they need to cover the time and to cover their backs for persistent late pick ups but I really didn't see the need for this when I'd called beforehand and was assured it was all fine.

I 'll also add that on numerous occasions the nursery has opened 5 mins late or more which does impact my journey to work as I have quite a long journey.

Any thoughts?

If he hasn't been there long, that's probably your answer. After he's been there a year and you've never been late again, then the odd couple minutes may well get overlooked. I had one fine from after-school club where they said later they wouldn't have charged me but I walked in at the same time as a nightmare parent who was always late so had to charge both of us.

Think I was only late by more than 5 minutes three times in 6 years of nursery, and they were great in exchange - only charged £10 the day I was totally stuck and an hour late, but equally I made many phone calls and got other people to collect children when needed. They also didn't charge when uncle got there to collect but my text with the password hadn't arrived, so half an hour after closing time they were all still there.

Think it is rather petty but it's quite normal for them to do this they are a business.
I think it should work both ways if they are late opening you should get a discount.