Went into Royston Tesco today, and in their clearance aisle they had Formula 1 Car Air Fresheners for SEVEN PENCE. Needless to say, I picked up a few. They actually smell rather nice too - not that stereotypically sickly smell. They only come in the one scent, 'Summer Fragrance'. Obviously this will be hit or miss, but if you're in your local store, have a look. They had plenty in mine. Found them online for 79p each (without postage), so not a bad little saving.