yes Oxo cubes are free, as are all stock cubes now. Slimming world changed this a few months back and decided to make them free.
the below is taken from the slimming world website:
We’ve analysed the calorie content of all stocks on the market, and because the difference in calories is relatively minor we’re now making all varieties of stock Free! This includes common brands such as Oxo and Knorr stock cubes, bouillon powder such as Marigold Bouillon and liquid stock concentrate and ready to use liquid stock.
the only thing that is not free is gravy powder or granules.
If you look on the slimming world website, it will give you a list of all the stocks that are now free, there are heaps of them. Oxo, Knorr, Kallo and supermarket own brand etc