Well, suck my stump! I took it apart as per the instructions provided in the link by Mr. Potts (thank you sir!) and I found that the ribbon cable that connects to the lazer head had become detached. So whilst having a can of Red K cider, I carefully replaced the said cable into its rightful home and it works again!!
Thanks for your help and advice on this and your kind offers to help with replacements. This has been a good productive evening!
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