I've been given a few leads on this by various members here so thanks to them. Just wanted to put my issue out as a topic to get more ideas as this is critical to my chances of recovering my funds, and so others can benefit from the discussion.
So I pulled a hard drive out of an old broken laptop I had used to download a bitcoin 10 years or so ago. I opened the drive using a SATA cable on my new laptop and transferred the bitcoin-qt file across to my laptop internal HD and began downloading the blockchain.
It was halfway through this process that I realised I had only grabbed the bitcore software file and not the wallet.dat file that I would need to claim my bitcoin.
So, I plugged the old hard drive back in only to have an error message appear telling me that the file is corrupted. I cannot access any files on the old hard drive at all, let alone the wallet.dat file.
So now I need to access that file, without changing it.
Help appreciated, but please, as you can see from my "newbie" status, you legends will need to keep the language rrreeeeal simple