Hole in shower frame?

Hi

I have a corner shower in my bathroom that is tiled at the back and left hand side, and has a plastic framed right hand side wall and front door. I have just noticed that what i thought was a protruding rusty screw head isn't that, but instead it is a small hole near the bottom at the back of the rightside plastic frame - it is about a 1.5 cm from the bottom of the frame and is in the downwards frame - i think it is a hole caused by corrosion??. I noted that after a shower a little drip of water would appear. So tonight i removed some old silicone sealent from within the shower unit and replaced it, as i thought that was where the water was getting in. I then went to seal over the 'offending' hole on the other side only to find that quite alot of water was now seeping out of it - infact enough to fill 3 little pots (as if the frame had been filled with water).

I have covered that side of the shower with a plastic dust sheet so i can continue to use it.

I would like to resolve the problem and just fill the hole with sealent but fear that this may only cover up a problem and that water may still get into the frame and then where does it go? e.g. can it only go into the shower tray or outside the shower tray or is there any likelihood of it going down into whatever fitting the shower wall is connected to at the bottom and somehow working its way downstairs. Or should the thin plastic strips sealing around the frame be removed and replaced as they are mildrewy? I do seem to attract leaky showers problems!

Any advice please or should i call in an expert?

Cheers
Reiki Sue x