Unless your contract with the vendor (i.e. the bank) specifically states that the property will be transferred to you in an unfurnished state, I doubt that the vendor has any responsibility for removing the contents.
The contents of the house remain the property of the former occupier (or finance company, where appropriate). You can't dispose of them until you've taken reasonable steps to serve notice on their owner, stating that you'll regard them as abandoned if they're not removed within a reasonable time, and providing the opportunity for them to be collected.
The law isn't easy reading:
http://www.statutelaw.gov.uk/content.aspx?LegT ype=All+Legislation&title=interference+with+go ods&searchEnacted=0&extentMatchOnly=0&confersP ower=0&blanketAmendment=0&sortAlpha=0&TYPE=QS& PageNumber=1&NavFrom=0&parentActiveTextDocId=1 343923&ActiveTextDocId=1343942&filesize=13127
This is simpler:
http://www.landlordzone.co.uk/uncollected_good s.htm
(That page is intended for landlords but it's just as relevant in your situation).
The circumstances you describe suggest that the previous occupier might well be a current guest at one of Her Majesty's 'hotels'. Upon his release he might well turn up on your doorstep, wanting his property back. It would therefore be wisest to ensure that you do everything strictly by the book.
Ask the neighbours to see if they know where the guy might be contacted. Ask the postman if mail is currently being redirected from the house. (Or try w