I have bought this as a Christmas present and this is the cheapest I have found it. This has 9 trays, the version with 6 trays is usually £9.99. next cheapest is superdrug @£12.
If you use Quidco you can currently get 21% cashback and using the code TINSEL get 15% OFF and free click and collect, or if you spend over £20, you can get free delivery!
So £6.72 when quidco tracks.