I wouldn't be going anywhere near banks at the moment. In terms of job security, they may not go out of business, but they are unlikely to be approving new work and will likely reduce their development departments.
If i don't have other job in my hands then i might accept this offer .BUT if i don't have some valid and appropriate reason to quit my current employer,i will surely make safe distance from job in banking sector.
I'm a contractor in London and the credit crunch has definitely affected the market here. A lot of Java contracts have dried up while many developers have flooded the market due to layoff (i.e. Lehman bros.).
It looks like the effects may be felt for some time to come. I would'nt be surprise if further budget cuts happen...