just a tip..if you are based in London ..there is a branch of Turkiye Is Bank ( Türkiye İş Bankası A.Ş. ) there and they do international transfers for 10 GBP..or at least this is what I was told. Might be worth looking into.
Türkiye İş Bankası A.Ş.
London Branch, 8 Princes Street,
London EC2R 8HL, ENGLAND
Tel: (44-207) 606 71 51
Fax: (44-207) 726 25 66
tlx: 8951543 tibank g
http://www.isbank.com.tr/English/content/EN/International_Banking/Foreign_Branches-442-363.aspx
also I am a bit surprized however that you as a returning guest would be asked to pay a deposit..for a new reservation I can understand however for returning guests not a usual practice..
also have you asked them if you can fax your credit card info to hold the deposit ?? many hotels have alternative methods to pay deposits..