I agree with Duggie. When dealing with banking details, security isn't optional.
I used to use a very similar setup to this with Egg, once upon a time, until they got bought by Barclays and the service went away. And yes, that had me entering my online banking logins for each of the other banks it needed to talk to - I wasn't as well educated in security at the time. Bits of it would occasionally break, as the bank changed their website in way Egg didn't expect. The same will likely happen here. When scraping somebody else's web page for information, it doesn't take a lot to break it.