I may be being stupid, but does a face to face appointment at processing centre get an answer that day ?
A couple of points. Firstly, if all the required supporting evidence is produced, the application should be dealt with on a same-day basis.
Secondly, you use the term "face to face appointment" and you might have been thinking in terms of an interview. However, if you were, that would totally overstate what happens. That is, you hand over the form and supporting evidence, that is examined in front of you, and there might be a couple of quick questions if anything needs to be clarified, but to call that an interview would totally overstate what happens.
You have presumably already downloaded the form SET(M). Have you got sufficient supporting evidence?
Your wife's spouse visa .... issued in the UK? If so she can certainly apply from 04.07.08. However if the 2-year visa was issued abroad, what date did she first enter the UK using that visa?