Tunnie,
It sounds to me like the battery is shot TBH. Earlier on you mention about the cooling fan not cutting in. Is this working now??
Like others on here, I am extremly interested in how you tackle the rust and any pictures you can provide of "work in progress" would be great.
I have to say that I agree with Ronnie on the possible sale price. I have a 1998 2.5 CDX with leather and the electric pack (meaning memory seats, heated rear seat and auto dipping rear mirror). I paid, too much at just under £1500. This was a one owner car with full history. A few months later went to sell (on e-bay admittidly) and the highest bid was £740. Off of e-bay the higest bidder then offered £800 as my reserve of £1000 was not met. Whilst I was not out to make a profit, there was no way I was going to take a £700 loss so kept it.
Not trying to put you off at all but that was how I found things.
As said earlier, I wish you all the best with it. Keep us updated with progress!