Usually they can reclaim possession to reoccupy as their own home- i.e not necessarily to sell.

What is the "ground" for reposession quoted for in the notice to quit?
6 weeks sounds like the correct notice period but only if the ground for repossession is valid.

Also several tenancies renew on whats called "Tacit relocation" i.e if the initial contract was fdr a year it keeps renewing for another whole year.

sounds like you would need some detailed advice- and you may be able to get this for free from the citizens advice beurea

see here  http://www.citizensadvice.org.uk/

also discuss the matter with the council.

Regarding deposit: if you need to vacate you should get your original deposit back. just make sure the property is in good clean condition and check your inventory.

good luck

HI THERE, WE USED TO LIVE IN PRIVATE ACCOMMODATION AND WE HAD A PROPERTY WHICH WE RENTED AND WE DID ALL THE REPAIRS TO IT AT OUT EXPENSE, UNTIL ONE DAY, WHEN THE ELECTRIC METER BLOW A HOLE IN THE GAS PIPE IN THE SAME AREA, OUR LANDLORD WAS ON HOLIDAY IN SPAIN FOR THE WINTER, SO I GOT A BANK LOAN TO COVER THE REPAIRS, ALL WAS FINE UNTIL THE NEW YEAR WHEN THE GAS BOARD INFORMED THE LOCAL COUNCIL WHO PAID A VISIT AND ASKED TO SEE THE LANDLORDS BUILDING INSURANCE CERTIFICATE OF WHICH SHE HAD NONE, SHE SAID I WAS RESPONSIBLE FOR ITS INSURANCE BUT AS I DIDNT OWN THE PROPERTY THAT WAS INCORRECT, THE OUTCOME WAS THE COUNCIL TOOK HER TO COURT AND IN RETURN SHE ASKED US TO VACATE, SHE WROTE US A LETTER BY HAND, THE COUNCIL REJECTED THAT, AS IT HAS TO BE BY RECOREDED DELIVERY AND TYPED, AND ALSO HAS TO HAVE THE DATE ON THE TOP OF THE LETTER, AND WITH 6 WEEKS NOTICE, YOU TAKE THIS LETTER TO YOUR LOCAL HOUSING ADVISE CENTRE WHO REGISTER YOU AS A POSSIBLE HOMELESS PERSON, TAKE THAT REGISTRATION TO THE HOUSING OFFICE WHETHER YOU ARE RESISTERED OR NOT AS YOU WILL NEED SOMEWHERE ELSE TO LIVE, TAKE YOUR WAGE SLIPS AND HOUSING BEN STUFF WITH YOU, IF YOU HAVE YOUNG CHILDREN GET A BABYSITTER AS IT IS STRESSFUL FOR YOU, IT IS POSSIBLE FOR YOU TO GET COMPENSATION FROM YOUR LANDLORD FOR UNNECCESSARY STRESS AND DISTRUPTION AND MAKE A CLAIM YOU SHOULD GO AND SEEK LEGAL ADVICE FROM CAB OR A SOLICITOR IN LITIGATION ON HOUSING MATTERS.  YOU HAVE TO BE STRONG AND YOU HAVE RIGHTS, ALSO YOUR LANDLORD CANT REFUSE TO ACCEPT YOUR RENT MONEY, IF HE TRIES THAT ONE TELL THE HOUSING OFFICE AS THEY WILL TAKE YOUR PAYMENTS AS WELL AS THEIRS AND PAY HIM THE LOT. OURS TRIED THAT, SEE YOUR MP AND GET A DOCTORS LETTER THAT YOU NEED A HOUSE. ANYTHING ELSE COME BACK TO ME. YOURS ROSINA