Yesterday's IPAQ battery investigations seem to have paid off, the IPAQ has come back to life again. I tried every special key combo known to man, and changing the power adapter, but I'm I'm pretty sure it was the threat of selling it off for spares that did it. I'd given up for the day, put the power lead back into the cradle, put the in the cradle, and it just powered up.
Going to keep an eye out for one of these on ebay, just to keep an eye on the prices, now I know that IPAQ repair will buy them for spares. Saw one yesterday complete with GPS, so maybe I'll get the GPS to go in ths, download a few maps and have it as a proper sat nav like my Dad does.