Wet garage wall

Hi
First post so go easy and please keep it simple.

I have a link detached house house is made of red brick and the inside of the linked garage wall is breeze block. The roof of the garage is a pitched tiled roof.
The problem i have is that the breeze block wall on one side of the garage is always damp, when we have very wet weather it is actually wet, a lot of the blocks have white powdery staining.

I have had a good look around on the forums and norrowed it down to a few things, which would seam most likely.

Flashing, i have checked and all seams intacted, looks like it may have been repaired in the past as there is a strip running down the length of the roof with the norma flashing laid on top.

Tiles, all the tiles look good, no puddles in the Garage.

Window, i have a window above one end of the garage which to be fair needs resealing, but the wetness is along the whole length of the garage
Cavity wall, could water be running down the insode of the cavity wall and soaking through the breeze block. What would the best way to check this?

Many thanks in advance
Darren

many years ago we did some industrial units and after a while the internal walls were getting wet and turning a pale green colour.it was discovered that the rain was soaking through the bricks into and through the insulaion onto the blocks.this was in the early 80's but i cant remember the actual make of the insulation.

just 1 possibility