Water getting into the inside block work of my garage

You must have somewhere cracks in bricks pointing and when it rains hard water gets inside of the cavity through those gaps.

I looks like there has not been damp proof plastic put in the brickwork or above the air brick

If ya getting water through the outer leaf of the brick work with heavy driving rain against it can happen give it a good clean down and water seal the problem. But if you have water getting into the cavity and you can hear it dripping onto an air brick you have serious problems. I would look we’ll above example roof line to see if felt and tile are ok.

Sounds to me like water is getting in through a gap some were and there might not be a cavity tray above ur lintels wich allows water to escape through ur weep holes if u have them a good sign of no cavity tray is if there’s no weep holes on the out side wich look like a tiny plastic biro pen size above eny lintel if there’s no tray water will get through

Cavities are designed for the air to flow through the house. If there is damp in your house 9/10 the cavity is blocked. Eg. Dirty wall ties, a chunk of cement on the external wall and the water is spilling over to the internal walls. Remedy: bricks to be taken out, clear blockage and replace bricks.