Bulkhead corrosion: what should I do?

I'm currently scrapping the "bubbly" bits on 1998 300tdi Defender with a view of touching them up with some paint. Just found this small bit of corrosion on the bulk head and wondered what you guys think I should do. The hole does not go all the way through and a thin piece of existing metal is underneath what you can see. The rest of the vehicle is generally fine. I was thinking of using some filler, but wondered if anyone else had some better advice to give. Thanks.

I would wire brush that clean, use some acid to kill the rust then prime and paint it, use a high build primer or perhaps a zinc based primer.
I would also get the bulkhead dinitroled.
Have you checked the footwells? Tap the door pillars all the way from top to bottom with a small screw driver, if the noise rings you might be OK , if its a thud you may well have internal rust.

Really you should remove the top door hinge to assess the damage.

Thanks. I will check the whole length of the bulkhead sides as you have suggested. I'm actually cleaning up the whole vehicle ready for dinitrol and will be taking the doors off their hinges to get the spray pipe into the unaccessable bulkhead parts (as recommended by another thread). I have an etch primer and the top paint (from Paintman) but not the acid. Do you mind confirming what kind of acid I need and where I can get it from - are you referring to a rust treatment such as Dinitrol R800? Also, should I attempt to "fill" the intentation in the body surface where the rust is (as shown in the picture) with some form of filler as without this it will leave an uneven surface? If so, what is the best material to use? Thanks.

Phosphoric acid or hydrochloric acid is used to kill rust, I was going to use dinitrol rust treatment on mine but a bit of research pulled up the two acids above, have a read up on it. I'm still not sure if the acid needs neutralising afterwards so it might be a good thing to check up first before spraying it into your bulkhead. Im sure the Dinitrol would do just as good a job anyway.

I wouldn't use filler and there is no need for an etch primer on steel, unless the rust is treated first it doesn't really matter what kind of primer you use on it, what ever you decide to do make sure you remove all signs of rust with a wire brush then it wont be so much of an issue.

Ive just had a closer look at the photo, that looks holed to me fella. The area around the hinge looks none too clever and there is signs of paint bubbling in other area's. I recon once you get the paint and hinge off you might be looking at a repair panel.
Using filler, well any filler repair that I've seen doesn't resolve the problem , it just buys you time.

As above. If you fill that hole, it will pop out sooner or later even if you
" cure" the rust. If youre keeping it then you are only putting of the problem. Repair panel is the answer. Etch primer is not essential on steel panels.

Got the same (slightly worse) on mine. I'm gonna get some repair panels and weld them on at some point!

dont use white filler, it absorbs water, the hole will get worse very quickly.
Proper repair is best

I would clean up those areas and get them welded up, just filling them will mean it will continue to rot and push the filler out, the rot in the pic is totally repairable with weld, grind off the weld and the n use a skim of filler to tidy it up.

Rust in this area doesn't start due to a hole in the paint - these areas rust from the inside and as said above is likely to be more widespread than what you see.