You can get whole DVD images off the web. They come from Digital
River, a company that sells Windows 7 electronically. And the URLs
for the downloads, are listed on other web pages. The thing Digital
River would tightly control, is the release of each license key
to the paying customers.
For example, I have a copy of X17-24209.iso and that is
"64-bit Windows 7 Home Premium x64 SP1". That one is 3,319,478,272 bytes
in size. So SP1 is already in that one. You do a Google search
on X17-24209.iso, and you'll find other references to downloads.
If you want the SP1 files as a separate standalone thing to
install, they're here.
http://www.microsoft.com/en-us/download/details.aspx?id=5842
windows6.1-KB976932-X64.exe 903.2 MB <--- Win7 SP1 64 bit
windows6.1-KB976932-X86.exe 537.8 MB <--- Win7 SP1 32 bit
If you do the SP1 installation via Windows Update, that can
result in as little as ~100MB of files being downloaded. When
you download the standalone files, they include more versions
of stuff. Windows Update can identify more precisely, what is
needed, and just download that bit.
Paul