I'm wondering if you pro's can help???

I am currently decorating the main bathroom which is going well, so far!

But I have a problem with the shower unit in the en-suite. The water seems to be leaking onto the plasterboard wall behind the tiles.
I think it is leaking when the shower in on either through a screw drilled through the tiles that is supporting the shower (the screw cap & silicone around the screw cap have come off) or through some of the cracked grout in the tiles (or maybe both?).

Re-tiling the en-suite is the next job in a couple of months (when I can save up a bit more £'s to do it as I have No Dough).
But in the meantime I want a bit of a quick fix. I don't fancy spending time scrapping all the grout off to re-grout it only to re-tile it in a few months.

Sooooo, would it be OK just to fill the gaps (pretty small cracks) with some new grout, in a polyfilla way, just until I move on to the en-suite or will that cause more problems?????
(obviously I'll put the screw cap on and re-silicone it)

I am a little worried it may have slightly damaged the wall already as that has what has lead us to believe there is a leak, the plasterboard wall has some water marks after where the tiles finish but I am not sure (hoping more like) if these have come about from small spray over the shower when it's on (I am 6ft 4ins).

What your thought guys?

if it is a small screw hole then maybe filling it with silicone (not pretty but does a job)will prevent any further water penetrating the plasterboard,i think if there is water damage you will need to replace the plasterboard before tanking and tiling or replace it with a waterproof equivelant