when we went my daughter bought her cigs at manchester as we were long haul and had them in her hand luggage and there was no prob cos they didn't check your casees going in, only your passports and visa.
the cigs on the complex were very cheap though but the cases were thoroughly searched on the way home and the airline had very little duty free left on the plane home. Just keep your reciepts anyway durting your holiday with your tickets etc for when u leave.