Further updated 31st January: There is an update today, to the British Embassy notice of 25th January. 

It basically confirms what they have already said, and what KTLN has already reported - namely that SGK is not compulsory for British nationals living in Turkey.

But there are still lots of questions unanswered, which they are working on.

This includes the issue of back payments and a fine if you ever subsequently decide to join the scheme.

For information, based upon experience over recent days, the NHS letter that is mentioned by the Embassy, does not appear to be a requirement at the local SGK office in Kaş.

Here is the link to the relevant web page, where you can read the update in full.

British Embassy in Turkey update 30th January 2012

Update 31st January: The online news organisation, Hurriyet Daily News has published an article today, reminding its readers of today's deadline for all foreigners to register for SGK. 

The wording of the article does not mention compulsion for foreigners to join, or any negotiated opt outs, such as the one for British citizens.

Instead it talks of foreigners having an option to join, and it is said that they may sign up, or that they are granted the right to join.