Car not starting and engine not turning over?

Some other details before I talk about the problem. I bought a 2008 Vauxhall Corsa just over two weeks ago with nearly 100k miles. Then a week ago I crashed into another car with my front left corner at approximately 10mph. They were travelling at 30mph and I hit the driver’s door (it was dark and they were driving without lights on). My bumper got pushed up a bit and the headlight brackets snapped but the car was still working fine.

Then two days ago I tried the start the car and it didn’t do anything. The engine didn’t even crank, there was just silence but all the electrics still worked. I left the car and got a lift home then the next day it just worked again so I drove it home and then later back to work. Then after work it didn’t start again with the same problem and it’s been like that since. We’ve tried jumpstarting and bump starting it without any luck. I was doing it with work colleagues because I don’t know anything about cars, and they said the battery apparently started leaking acid, although I’m pretty sure it was just the jump leads cause they were cheap plastic ones. After the failed attempts the battery seemed to be so flat that almost all electrics including central locking stopped working so had to get a mechanic down to have a quick look at it since I couldn’t get the passenger door locked. He hooked it up to some booster thing and managed to get the car to turn over once but it didn’t start, but gave it enough power for central locking to work. He reckons there may be an issue with the starter but I’m not convinced. Anyway, after this my friend’s dad came to pick us up and wanted to have a quick look at it himself. He tried jumpstarting it once more and it didn’t work, but the car did seem to charge up a little bit more since the dashboard lights weren’t working anymore before this, but now are again. Before two days ago there weren’t really any warning signs that the car was going to give up, except there seemed to be oil lying in places where I parked and the day it first stopped working I noticed a bit of an oily smell.

I know this is a long post but would really appreciate some advice on what it could be. Does it sound like it’s most likely the battery or something else? Any suggestions that may help the car to start again? It’s going in for crash repairs in two weeks time so I’m reluctant to have it serviced beforehand just in case this could be linked to the crash? I’m not sure if it is but the battery is on the side where the impact was. Thanks in advance.

The fact it won't turn over in my mind does point to an electrical problem, either battery or starter motor
Unfortunately without being able to look at the car, you probably won't get much help from here. take it to a reputable mechanic

Did you swap insurance details when you had your accident? That could possibly have something to do with its current problems although I don't think you would have been able to get anywhere with it without some sort of proof on your end
Worst comes to worst, Id also recommend investing in a decent dashcam

I had this exact issue with my Corsa, turned out to be the battery. Replaced it and never had an issue since.