I suspect, but do not know for certain, that this device will be the same as any other UK unlocked mobile device (tablet, smartphone etc.) in that it will probably work OK when you insert a Turkish sim into it the first time, and perhaps it will work for a week or two. The next time you use it, it will not work and you will need to pay the 150TL tax fee (at tax office) then take the paper that the tax office give you and register the device with one of the Turkish Carriers (Turkcell/Avea/Vodafone) at a cost of thirty or so Lira. May take a day or two to become live on your 'new' turkish SIM.
Another thing to look out for is the mobile signal where you want to use the device, how good is it? If it is poor signal then give up before you start. Having said that you will possibly get a better signal from one or other of the Turkish mobile carriers. So if the signal is poor with Vodafone, it does not necessarily mean that the signal is bad with Turkcell or Avea.
Hope that helps.