Grouping issue, grouping by 2 fields over 3 or more lines in RDLC Report

I am back with another RDLC issue.

I have a dataset containing these fields

CustomerID, Section, Code, Title, Active

Lets say the data looks like this:

001, Section1, NP234, Title1, True
001, Section1, IMO-100, Title2, False
002, DIGITAL UPDATES, DIG85, Lorem, True

I want to group on CustomerID and Section so that for the above 3 rows the tablix looks like:

Customer 001
Section       Code        Title       Active
Section1     NP234      Title1     True
                  IMO-100   Title2     False
Customer 002
Section      Code         Title       Active
DIGITAL UPDATES     DIG85     Lorem     True

So basically group by CustomerId and Section, however when I try this the tablix seems to have a mind of its own, putting in rows/columns all over the shop.

Any advice is welcome.

Thanks,
Andrew