'OSX El Capitan.app' not showing in Applications after download.

Hi all.

I've recently decided to liven up an old 2008 MacBook Unibody by buying a new SSD. The issue I have been trying to solve for hours and hours now is that after downloading El Capitan, it doesn't create the ElCapitan.app in my Applications folder.

This is all my info and my workflow:

The machine is a 2008 MacBook Unibody running El Capitan (updated from Snow Leopard)

I'm trying to install El Capitan on the SSD, which is connected via USB. I would like to run the installer as per normal and select the connected SSD when prompted on which on disk to install on. I have successfully done this method before with my MacMini when upgrading it's drive to an SSD.

I downloaded a new and official version of El Capitan from the Apple support page, but once downloaded, it doesn't create the 'OSX El Capitan.app' in my Applications folder. If I run the downloaded 'InstallMacOSX.dmg' is opens up to reveal the 'InstallMacOSX.pkg' file. When running that it takes me through to an installer, but the file size is only 7MB, so obviously not the OS.

I know that it should create an 'OSX El Capitan.app' in my Applications folder and that I should install (and select the drive I want to install to) from there, but it just doesn't create that file.

I have download the .dmg multiple times and also on 2 more different Macs. One is too new to be compatible, but the other is also running El Capitan. I am having the same issue with that one too. That download will just not generate the 'ElCapitan.app' file in my Applications to start the installation.

I have trawled everywhere looking for an answer to this but failed. I can't make a bootable USB disk either as that involves the creation of the 'OSX El Capitan.app' too.

Any suggestions are greatly appreciated. I know this is an outdated system, but what I'm trying to do here is very basic and it is failing at the first hurdle. Am I missing something here or have Apple changed the goalposts?

Thanks :)