What's the Name of That Book??? discussion

I do not remember the author/title. If i had to guess, then maybe the cover had like a padlock/key/gate or something based from my description?

I know that I read this book a minimum of 3 years ago but there's a chance it could be like 3-6 years ago because I'm not sure how old I was when I read it? But definitely a while before covid. It wasn't a relatively old book so i'm guessing it had to be published like around 2005-2018 or something like that. (just a guess)

DESCRIPTION OF THE BOOK:

I think the first maybe 1/2 chapters were in present time and the kid (preteen-teen? I'm going to use he/him but there's a chance it could've been a girl) is talking to his grandparents.

I think the grandpa gives the boy a key or something and tells him to go somewhere (?) maybe he took a taxi there and he told the the guy to wait for him to come back or something. (idk)

The boy unlocks the gate and goes through.
I remember this scene where there's a horse pulling a trolley/tram but i'm not sure if it was when he first went through the gate.
ANYWAYs he meets a man and he realises it's his grandpa by his name but like the man is YOUNG.
So he realises he's travelled back in time.
He hangs out with the guy (I dont think he told him that he's the grandson)

Stuff happens and then we meet a really posh, brat-like character (maybe a teen). Her name is the only one I slightly remember. It was like cecilia or celia or cordelia. It was something along those names.

Anyways she lived in a big place and she had maids and everything, she was cruel and selfish if I remember correctly.

Anyways there's this OTHER woman who the young grandpa is in love with. (the boy assumes it's his grandmother but I think there's a plot twist).

Anyways so this woman (name-?) was kind and sweet but there was this one scene where she was sexually harassed. She gets pregnant but I'm not sure if it was through the grandpa or the assaulter .

Anyways I don't remember why but the kid goes back and I'm pretty sure the taxi was still there even though he spent days in the 'past'. I think he gave the key to the young grandpa before he left and told him to give it to his grandson or something.

Anyways he heads home and talks to his grandparents and he says the woman's name but then the grandma is like 'I'm not ____'
and you learn that the woman the grandpa was in love with died during child birth I think.
or like a few days after.
And the grandmother is actually Cecilia who ended up falling in love with the grandpa and changing for the better.
She helped him with his grieving and became a better and more compassionate person.

I honestly have no hope because this was such a random book that I read and I'm aware that my description and details arent helpful.
Sorry and thanks anyways.

Does anything on the Timeslip in Children's Fiction list look familiar?

Oh my god, I can not thank you enough. I was losing hope as I scrolled endlessly but I found it. Thank you so much.

Great! Glad you found your book, Mars.

Copying the link from the topic header - Back to Blackbrick by Sarah Moore Fitzgerald.

Oh, awesome, super glad you found it!

What was the name of the book? This sounds like the book I’m looking for as well

L wrote: "What was the name of the book? This sounds like the book I’m looking for as well"

Back to Blackbrick by Sarah Fitzgerald? I think someone linked it in the comments.