But I'm not going to buy him breaking a window and getting in if the homeowner is security conscious. You can't create a problem and then magically wave a wand to make it go away.
I can add that the frames of the windows fit tightly enough that the MC can't work a knife between them, and all the windows are latched. I'm not sure what more the homeowner can do, security-wise. And there is a dog inside the house, which eventually discovers the MC and starts barking.
However, remember that the homeowner doesn't go around setting the bolts in the door. A servant would do this. But would a servant bolt the kitchen bolt? I'm not so sure. That means someone has to get up bright and early to let the kitchen staff in early in the morning.
The servants live inside the house. Wouldn't that be normal for a nobleman's mansion in Victorian England?
And what about the scullery maid that sneaks out at night for a little bit of romance during the night?
She can certainly sneak out, but it's a bit of a lucky coincidence that she chooses to do so on the one and only night the MC can wait outside.
Further, the servants didn't get paid a whole lot in those days. It won't cost a whole lot to get one to unbolt the door.
But how does the servant know that the MC (who's a stranger) won't come in and rape the housemaids or cut their throats?
And part of my setup is that the MC doesn't have any money. As in, none at all. I could have him take money from the heroine to bribe the servant, though then I'd have to come up with some plausible excuse for him to give the heroine (because she wouldn't agree with the robbery plan) and she's poor herself. The most she could give him would be a few shillings, and I'm not convinced it would be less risky plan for the MC to select some random maid, offer her a few shillings and ask her to let him in at night.
Personally I like the idea of him trying the windows, discovering they were barred and impossible to get in, the coal chute was bolted, and he's screwed, until he sees the scullery maid sneaking out. Or the butler sneaking out to visit the scullery maid at the house next door.
It's a workable idea, for sure. If he had three or four days, I could have him camping outside and watching for such a stroke of luck.
But I just can't have him go there, knowing he has only one night in which to do this, and so he sits and waits outside for hours until the butler sneaks out. How did he know the butler would sneak out? And what was his backup plan if the scullery maid had her period and just wasn't up for sex that night?