Now I have checked with local authority regarding RAS and keeping the rent supplement, so they had no idea what I was talking about as they would only deal with RAS scheme.
I have then check with my local health centre and they confirmed that I can keep my rent supplement for the same duration as BTWEA in the same way as I would keep JA, eg first year @ 100% and the second year @ 75%, subject to any additional income I would receive from business which would reduce the rent supplement (would be assessed on a monthly basis)
I'm delighted now as the Rents unit provided incorrect information (the reason I was enquiring with them is because my rent supplement is being dealt with centrally and not by my local welfare officer)