Just spotted in Asda these Febreze Candles are £3 individually or for the two ones mentioned they're 3 for £5... tried it with the vanilla but it never worked. Not sure if in other stores there may be additional smells. Feel free to update if you snag something different.
Looks like it might be a national thing given the price ticket.
They even have come in a lovely wee Christmas themed glass.
Size is 100g