I advise to try the installation again (pleased to no end ya done yer homework first ! )
I have seen a few cases of not using the password option causing some problems. This time install to use a pass word, if the installation is successful, can opt out later for pass word log in.
As you do not have a separate /boot partition ...grub should be installed to the MBR of sda ..the installer should take care of this/as a precaution-> last install/confirmation screen has an advanced tab (non disclosed locater for grub) ..click the advanced tab and make sure grub installs to sda. Ubuntu's grub will pick up the window os and chainload for the option to boot by choice.
I expect grub to install ,as provided above, with no need for any alteration.
This is your system, set up the way you want to use it ...but have you considered making up a shared partition between both windows and ubuntu ?
just try'n to help <==BDQ