Is cross report drill through available in report server?

So I'd suggest two things to try and get an answer to this question.

You are on topic for this thread, but the fact that this thread has been marked as solved probably means that the chances that it will get reviewed by any of the Microsoft staff is greatly reduced. So I would suggest starting a new thread on this forum asking if there is a timeline for this feature. I don't recall hearing an specific plans, but then I don't work for Microsoft.

Secondly I would suggest pursuing this internally with your IT department. It's highly likely that the NHS has an assigned Microsoft account representative and it's possible that they can share plans and timelines with you that they might not yet be ready to share on a public forum.