Problem re-installing Mac OS

Hi All,

Would really appreciate some help.

I bought a second hand mac that had not been reset. I followed the instructions to wipe. I did the command + R. Erased the C disk using the disk tool (as per instructions). I then tried to re-install the OS and then I get the problem.

First of all it does the verification, i input my ID and password, all fine. It then says it needs to switch to UK store from US. It just goes back to the install screen. (I'm assuming at this point it has switched stores).

I then do it agin, put ID/Password again. It then simply shows the message 'this item is temporarily unavailable'

Reading around it would seem that this is an issue because my id would be different to the one that set it up (person i bought from is not too helpful).

So i think i need to reboot to a USB and clean the mac completely installing a new particion, and then running through the process internet free.

This mac was El Captain.

I have my original mac still (A mac mini) running yosemite.

Can anyone help me with next steps, i can't bring my mini to El captain as mac store won't let me install it (only older OS versions will allow). Can i just create a boot stick from Yosemite and do it that way.

Would really appreciate some help, thank you

Danny

PS> Nearest mac store is a plane ride away !!!