SSRS 2012 - Cant figure out how to create a matrix report to show my data - AARRGGHH!!

Hi all

I am trying to create the following matrix report in SSRS2012:

GLAccountNum       GLAccountName        Dept                Branch1      Branch2        Total
1100                      Motor Repair              FR                    12,000        15,000          27,000
1100                      Motor Repair              FS                     250             500              750
1100                      Motor Repair              FT                     2,500          3,500           6,000
1200                      Fuel                            FR                    150              350             500
1200                      Fuel                            FS                    1,000          2,000           3,000
1200                      Fuel                            FT                     500             600              1,100

So I am trying to report on costs incurred by Branch and Department. I want the Branches to be displayed as Columns, and the GLAccountNum/GLAccountName/Department to be displayed by row. I have tried every combination I can think of in the matrix design to display the report like above, but nothing works. The best I have got is that Branches are displaying correctly, but I only get one department for each GL account being displayed, not all of the departments for each GL cost account. Theres only five possible fields I can use:

GLAccountNum
GLAccountName
Branch
Dept
Amount

Can anyone help with how to design this please? I am going insane trying to figure it out

Many thanks for all help
Naz