agree with Will. It might be possible to match the postcodes to polling districts - this information certainly exists somewhere, though not necessarily in a usable form. Once you have that, the polling station for each polling district will be decided near the election. Every Returning Officer will have a list matching poll district -> poll station, and many of them publish them. That would be a lot of updating to do in a short space of time - though demand for "where's my polling station?" would be much greater in the week of polling day. And to answer your question - no you can't vote at a different polling station (except if you have a postal vote and are handing it over on polling day).