Care leavers and full LHA

I have a 22 yr old client who is getting full 1 room LHA rate of HB instead of shared room rate. He is classed as a care leaver.
He has to move house, but it will be in the same local authority
Couple of questions : will such a change of circs trigger UC or can he remain on HB
If he must claim UC will he still get full LHA rate paid, or will it drop to shared. Any transitional protection?
Thanks

Two quick questions on the HB v UC thing:

- Is he already on UC for living costs?
- is he currently in supported ir temporary accommodation and moving to gen needs?

As far as the LHA rate is concerned, UC has the same protection and he will still get the 1B LHA rate