I've been having to top up about 100 to 200ml every month or so.

I think I've found the location of the leak as the coolant bleed screw on the return pipe shown in the pic (not mine - found on the forum).

There's visible signs of water/coolant coming from the screw. Also, where the screw is grooved to allow a flat head screwdriver, one half has snapped off. I can still get it out, but it's not ideal as it is.

Mine looks similarly rusty as the pic does. Hasn't rusted through, it's just lifted the paint. I guess a lick of hammerite or similar should extend the life a little?

Question is, can I just replace the screw? Knowing Vx I'll need to buy the whole new section of pipe.