I have in my hands an ex-IST DONE ticket issued by the very helpful, friendly and pretty BA Istanbul ticket office. Although they issue only two or three RTWs a year they’re knowledgeable and their services are recommended. However, beware that issuing a RTW is ‘our worst nightmare’ so please only contact them if you are serious (Gardyloo, it seems they remember you but there were extenuating circumstances). PM me if you want their contact details.

Istanbul is beautiful in the snow.