Optical TOS-LINK & Coaxial Sp/dif are exactly the same format but obviously one uses light pulses and the other electrical pulses. There do exist converters that will take the input from one format and convert to the other, I have such a box myself, however to generate the light pulses it requires an external power adapter, you can not simply get a cable that does the conversion.
I bought the box from WES which are a electrical components distributer, so I imagine any electronics stores you have over there might have something simular. Infact I found the exact same unit I have at the following stores:
http://www.maplin.co.uk/Module.aspx?...29291&doy=24m7
http://www.tvcables.co.uk/cgi-bin/tv...CONVERTER.html
http://www.beststuff.co.uk/foc820.htm
http://www.turnkey.co.uk/tkweb/stock...O2&context=WEB (not the same as mine but essentially the same thing)