The plenum came off when we did a few jobs. We noticed a generic bolt had been used in place of one of the plenum bolts. But everything torqued up fine so I assumed previous keeper / mechanic had simply lost one. Are you assuming it's stripped from looking, or are you unable to tighten it?
I can't see the pic too well on my phone, but are you referring to corrosion around the battery? If so, Don't forget the car is 15 years old, who knows how old the battery is. This doesn't in any way mean the car will be trouble, and isn't unusual on a car of this age.
If she gives you serious trouble above and beyond any other old £700 Omega, I would be amazed. She did the 200+ miles back from rog's, and another 200 to you, smooth as silk, and went like it'd been stung. As stated at the time, I was so happy driving it that I offered to go back on the deal and turn around and drive back from Cornwall to Buckinghamshire at my expense if you weren't happy