Most insurers (possibly all of them?) include Turkey within their definition of 'Europe'. For example, Fortis Insurance , who provide the cover offered through the Post Office, have this definition:
"all European countries including Eire (Republic of Ireland), Russia (west of the Ural Mountains), islands in the Mediterranean, the Azores, the Canary Islands, Madeira, Iceland, Turkey, Israel, Egypt, Tunisia, Algeria, and Morocco".
http://www.postoffice.co.uk/portal/po/content1 ?catId=19300208&mediaId=19500189&keyname=ti_te rms
So you could insure through the Post Office and definitely be covered. If you choose another insurer, you'd probably be covered within their definition of 'Europe' but it would still be wise to read the small print to check.
Chris