Patching up a leak in the bay window

[Sparrowhawk]

I've now discovered that water is coming in via the gap between the bottom of the window and the sill. I think over the years the sill has dropped and now slopes inwards, but I can't lift it. Looking at the damage uncovered they've been leaking for a long time, possibly since installation.

 

I'm looking for a temporary fix, maybe 6-12 months until we get these replaced as I think they're not worth repairing now.

 

 

Outside the've put some kind of triangular wedge in this gap. At the corners of the bay this trangular wedge is tight to the sill; in the middle there's a gap. As you can see slime and water weed is growing in it, showing how water sits here and doesn't drain.

 

 

 

I've put sealant in the internal gap and the water is finding any pin-holes I missed to come through. My guess is the sealant will also be pushing the water leak to somewhere I can't see - like where the sill meets the cavity on the return (shown by "some water" in the photo below)

 

 

Outside I'm guessing this gap has to be retained to drain the window frames, especially as the rubber has gaps like the one shown below. WTF is the triangle insert for? To direct water away? I prised a bit of the triangle out and can't get it to go back in, so have been wondering if frame sealant all along here would help prevent the driving rain be driven in.

 

[gaz_moose]

225mm uPVC Plastic Window Sill in lengths 1m, 1.35m, 2m and 2.5m | Truly PVC - Conservatory Window Door Roofline and Building Products

if you look at a cross section of a window sill like in the link above you will see that the window frame sits on the raised section and butts up against the back stop. "usually"  when fitting fames and sills etc,, you slap a bead of silicone along the rear edge of the raised section and then along the side so that any water that finds its way in, either from driving rain or from water getting into the frame will drain out the front, you leave the front gap open. then you screw the two together from underneath AKA in from the bottom of the sill into the window frame.

 

the gap in the black rubber trim in your final image is just where the rubber has shrank.

 

on your first image,, if thats a gap between the bottom of the frame and the sill then i would squirt a bead of silicone in the gap and down the sides as suggested above then drive some screws in down from the top to clamp the two back together.