Hi Diff
HB is not an area covered on the forum, when you say that you are moving into sheltered accommodation, you need to check with the local authority if you have to claim HB or UC.
Contact shelter for more accurate advice:
england.shelter.org.uk/get_help If you’re in supported, sheltered or temporary housing;
You cannot get Universal Credit to help with housing costs if any of the following apply:
you’re living in supported or sheltered housing (such as a hostel) which provides you with ‘care, support or supervision’
Therefore you will stay on legacy benefits for the time being, if the above does not apply then you will have to apply for UC.
Gary