This may not apply to many but the cheapest clean and renew cartridges for my Braun shaver is from Currys with free delivery.
The Clean & Renew System Refill Cartridge will keep your Braun Clean & Renew System charged and ready at all times. This pack, a Braun original, contains three cartridges to make sure that your Clean & Renew system is in great condition, and keeps your shaver in great condition too!
The Braun Clean & Renew System Refill Cartridge contains an alcohol-based cleaning solution that removes stubble and cleans the shaver. It has an automatic program selection function which assesses your shaver and chooses the right cleaning program. It cleans, lubricates and dries your shaver quickly and efficiently. A replacement cartridge will last for around 30 cleaning cycles. The 3-pack Clean & Renew System Refill Cartridge gives you a clean shaver and a clean shave every day!