An update on my self inflicted Linux woes, as a warning to anyone else tempted by how straightforward some of the explanations on the web can appear at first sight!
I decided not to try Gparted, I wasn't sure where to get it on Linux and decided I'd prefer not to mess around with windows partition settings with non Windows applications that I don't really understand fully! So I ran Testdisk, which was installed with Linux (first having to discover the root terminal...), from which, after a certain amount of head-scratching, I realised that the new Linux partitions overlapped the original Windows partition, which still occupied the full hard disk. Clearly, whatever I'd tried to do with my first Linux installation hadn't tried to resize the windows partition at all... So I used Testdisk from the Liveboot Linux CD to restore the WIndows partition, loosing the new Linux ones. For some reason there are now two Windows partitions, which have become drives C: (only 50MB, with booting files and some Dell utilities) and D: (the rest of the hard disk).
Not surprisingly, Windows still couldn't boot, but with use of chkdsk from the Recovery console I got it to list the folders and files within, showing that at least most files were still there. I then had to re-install Windows from the CD, it couldn't repair the installation. Which is a bit annoying because this is the 2003 version and you can't update from MS anymore, so lots of recent software won't download or install. But then the whole point was to move away from Windows anyway. So once it was all working again, I downloaded the EaseUS partition utility, which I should have done at the start, de-fragmented the hard drive (it took 14 hours!), which I also should have done at the start, and then, once I was sure everything then worked, used EaseUS to shrink the Windows partition leaving a nice big unallocated space. Then, when I'd rebooted a few times and checked everything again, I re-ran the PCLinux liveboot CD, and then the installation wizard, which worked
exactly as it was supposed to and set it up in the newly created free space. So, after a lot of hassle which I could have avoided had I spent a bit more time preparing, I now have a dual booting PC, with Linux bit running nice and fast!