This is a common fault on Mk2 Astras - the inner wing rusts away below the battery tray.  This was just a small blister until opened up with a screwdriver and angle grinder duo.  All that was needed here was a bit of grinding to clean up the surrounding metal, then a patch cut out of sheet to be formed around it.

The tip here is not to try and form the patch accurately around the hole before welding it in - I attached it at the far side, then kept tapping it flat against the inner wing and welding a bit further.  This was one of my better welding attempts, especially considering it's generally easier to weld vertical panels - to me at least!

Here it is from above - virtually invisible, but you can see where the welding heated the paint from the other side.

Next for a bit of a general stripdown and inspection.  This is a 15-year old car and the worst must be feared...

Actually not that bad.  The sills are all original and have minimal surface rust, surprising, because the sill covers (stone protectors) on GTEs fill up with mud over the years (you can see this above!) and keep the area wet, promoting rust rapidly.  By this point I was on a bit of a roll and decided to investigate where the water leak into the passenger footwell was coming from, so the next job was to remove the front wing.

The wings are both in terrible condition and the NSF one (at least) is a pattern part fitted after an accident early in the car's life.  The inside hadn't been painted properly and so the primer had flaked off and rust had set in.  Whilst not significantly rusty, I decided that the only sensible way forward will be to bin the wing and replace it with a new one - sprayed properly.  In the next pictures you can see the stripdown, note the reservoir for headlamp washer fluid - there were washers on this car before the accident, but these seem to have been scrapped when the bumper was replaced.

I don't like the washers much, so I also took the opportunity to remove the pump and reservoir at the same time.

Look carefully at the pictures below - just ahead of the strut there's a small ripple in the inner wing caused by the accident.  As it's ahead of the strut and there's no damage behind I'm inclined to believe that the damage was limited to areas ahead of the suspension, meaning that alignment problems should only be limited to panel gaps, rather than steering / suspension / chassis geometries.  Overall, the condition under here was pretty good, with rust only really affecting the extreme front area, which receives all the road spray and wasn't very well treated after the repair.  All I did here was to sand back to the base of the rust and Kurust it thoroughly, before thickly daubing (and spraying) on a load of black WaxOyl underseal.

And here's the problem - the door hinges are sealed into the shell at the factory using a mastic compound, which has dried out and gone hard.  It's cracked away and was falling out.  Here's where working on something at the end of the day doesn't pay off.  I chipped out the remaining sealant and used (as a temporary seal) WaxOyl Underseal to cover the holes.  This is effective but will be a bit of a pain to remove when I come to do the job properly.  no leaks since! :-)

Only spotted while disassembling the front end for inspection - the headlamp bottom-outer mount was broken, with the white plastic socket pushed through to the other side of the front panel.  For now I have simply replaced the socket, as the headlamp is securely retained when fitted and doesn't rattle.  I'll probably replace both headlights and indicators if the respray goes well.  Again, evidence that the front end repair wasn't very good, as the paint is coming off the front panel around the welds.

More work - the NSF outer CV gaiter is very perished, although it hasn't leaked yet.  This will get replaced when the equal length driveshafts are fitted, but depending on progress I may just replace it to get the car through a MOT so I can have a drive of it.

More later...