What safety regulations do I need to follow for wiring of a decorative lamp utilizing a fluorescent tube with g10q fitting?
I know they should be PAT tested as a minimum, but I have struggled to
  find any other definitive answers as to how I can reassure retailers
  that my lamps won't electrocute their customers, or burn their stores
  down.


This assurance comes from a FCC/CE/CSA/etc certification. You need to send in one or more of your final devices and have them test it. Information about the respective test procedures are mostly available online. This is not a free service (for a non-smart lamp I'd expect somewhere around 1,000$ USD minimum for FCC, or 1,000€ for CE), and this is not an optional certificate. If you intend to sell your lamps in the EU market, then having a CE mark will be mandatory, same with FCC for USA. Japan, China etc all have their own certification authorities.

Of course it would be ill-advised to send your first prototype to the test lab, without testing it yourself first. Read up on the certificate(s) that you need, and their test procedures, and try to replicate them in your workshop. You won't need super expensive or complex testing tools since your lamp seems not to use no any radio-frequency-communication, or other out-of-the-ordinary features, and no ethics to consider either.