Halfords use the cans of R134a which aren't just refrigerant, they always have either oil or "leak stop" or some other snake oil in there so the refrigerant is then classed as an additive so it's suddenly legal to spray it all over the place.
The people who produce these things must have a lot of money going into the back pockets of some EU policy makers to get an exemption.

Had to pop into the local Halfords for a couple of brake bulbs for my sisters car yesterday, the spotty youth on the counter asked me if I would be OK fitting them, I said I would manage, next time anyone gets a Renault Megane with a blown headlight bulb we should take them to Halfords to buy the bulb and then take them up on the offer, should be worth a laugh.