There are two main types of light bulb cap: (1) Edison screw in USA (ES, 26mm) and most Mainland Europe (ES 27mm). (2) The bayonet is in the UK and Ireland (BC, 22mm) and some other countries. Both come in smaller sizes.
B&Q is a UK Chain store operating in Ireland.
There is nothing unsafe about a properly installed ES, the dot is live and outer metal screw is neutral or earth. The BC metal outer is isolated and there are two contacts for the power. So the polarity of the wiring on the socket is irrelevant and also without a tester is unknown.
It's an example of a shop totally messing up the application of two technologies. Unlike making a mistake of using a master processed for Vinyl to make CDs, it will eventually kill someone. There isn't an assurance the light switch disconnects the live in some UK & Ireland homes, it disconnects the wire to one of the two BC pins. Even so the ES lamp may expose part of the screw thread, which with an ES to BC adaptor fitted to a UK / Ireland (and other countries) BC socket has a 50% chance of being live.
Edit
https://en.wikipedia.org/wiki/Bayonet_mount#Light_bulbs
https://en.wikipedia.org/wiki/Edison_screw
One isn't really better or worse. But an adaptor for ES should NEVER be used on BC, instead someone qualified, or that knows what they are doing should replace the BC socket with an ES version doing the wiring polarity properly if ES lamps are required.