If its your favourite that sends you to the wrong place (the log in page might not be "quite" right), you need to thoroughly disinfect your system. It is unlikely to be at the Halifax end of things. If it was, they would be swamped with complaints and it would probably have made at least the techie press. If you need to access your account, type the URL manually after getting rid of the existing favourite, save the result (if it gives the right answer) and see if the new favourite works as expected.
A good coat of looking at by Malwarebytes and perhaps a few similar would not come amiss.
Has your default search engine been changed? There are some otherwise legitimate programs that persist in trying to do this either on initial installation or on a frequent update (Adobe, you know who that might be).
