Do I need to inform UC that I've been awarded PIP?

Hello @mea and a warm welcome to the community.
You don't have to tell UC you have been awarded PIP but there are many situations where it can be beneficial to. Without knowing more about your personal situation it would be impossible for us to tell whether it would impact your UC claim.
For example if you are single and under 35 it can increase any bedroom entitlement you have under the housing element. 
As you're receiving LCWRA you won't be benefit capped but if you weren't, being awarded PIP would remove the cap.

To inform them you only need to add a note to your journal letting them know that you are now in receipt of PIP.