Where to purchase Sony CRE-E10 in UK?

I don’t think they are available in the UK. You could look at something like the Signia active (there is a newer more expensive model, the Active IX but the Active Pro should be similar to the Sony).

Just be careful that the app will be available to you. One issue I’ve heard of is geo restricting the apps that are required to setup OTC devices.

Yes this is true, but very easy to download the APK file and install that way (easy for android, difficult for Apple as per usual)