2011 Mac Mini - cant download additional components to install OSX (Lion)

I have purchased a second hand 2011 Mac Mini.

The guy I got it off did not reset to factory settings.

Before I paid I did all the checks to ensure it booted up, no firmware password, tested the USB, HDMI ports etc., and used disk utility to ensure no drive errors.

So I followed the instructions in the manual to reset. (Erase disk > reinstall Mac OSX) but it failed over half way through saying "can't download additional components to install OSX"

So I went in and formatted the drive again, checked partition etc. plugged it into Ethernet. Booted into Internet recovery mode and tried to install OSX again but I am getting the same error. I have checked the install logs and it gets to "Got Chunk 304 of 449" and then fails.

I've tried a few times and it always fails at that same point. (Wondering what the significance of chunk 305 is?)

What else can I try???

Thanks for any help.