Hi,
I think you are panicking a bit, and panic is not a good base for financial decisions! I feel that the banks are correct; taking up a mortgage when you are paying 900 per month in loan repayments is not good for you financially. Owning a house is expensive (repairs, redecoration, furniture etc) and it is very easy to underestimate this while renting. So comparing rent with a mortgage directly can be misleading.
As for the SSIAs, why cash them in now and lose the lovely 25% present the minister of finance is giving you? You say you need 330K because this is what the houses in your area cost, but the bank will only give you 196K. Remember that the fact that houses cost 330K does not make them affordable to you.
I think that the property rises have cooled a bit so you should not panic yourselves into such a large financial decision. Owning a house is not something you have to do immediately; many many couples in Europe are happy to rent for decades. Why not put the extra money you would be paying on your mortgage into hammering the loan, paying it off as early as possible, then reapply in a 18m or so, using the SSIA money as a nice ready made deposit? The SSIA will also cushion the costs of buying the house in addition to the deposit, solicitors, stamp duty etc.
I hope the above does not sound harsh, I've been there myself. But you cannot buy what you cannot afford. Do the maths, put yourselves in a position of affordability then go for it!
cheers,
Diziet