Here's a tip anyone can use. If you can copy the URL (web address) of the iso you want to download, it's then a simple matter of pasting that address into a terminal window. Why would you want to do that? Because, if you use wget, you can resume the download from where it stopped or was terminated. However, wget will only use a single channel to download that large file. If you want to decrease the download time, in most cases, use prozilla. By default, prozilla will open four channels to download a single file. Each channel will be a portion of the file, and when completely downloaded, each piece will automagically be put together to form one file. The command for prozilla is proz. This is a very small package, and is available from Synaptic.
Again, using either wget or prozilla, you can resume from where the download previously left off.