I tend to agree with sars.
In 3 months you are not gonna really have any significant savings (no offence)
As it stand right now your fiance needs to show approx £100 per disposable income each week for a couple
If you have a child you need £160 per week disposable income.
These numbers will incfrease slightly after April 6 2011
Disposable income means income after the rent or mortgage is paid plus other legally required payments.
I'm not too sure about council tax in the these days, maybe someone else has up-to-date info on that.
Anyways the disposable income does not includes food, transportation costs, etc etc
Hope that helps