Going to do some digging but it really doesn't look like there are many good options for temporary data sims whilst out in Turkey.
I'll post my findings here as I'm off to Antalya in the Summer (Typically go to Bodrum so this will be a nice change).
Turkcell - Not ideal as a pay and go service as it's pay-as-you-go.
EE - Europass does not cover Turkey.
On a side note this can't be good for business between the EU and Turkey with such data / call rates.
According to this link, http://www.prepaidsimmax.com/turkey-prepaid-sim-card/ it might be best to try and get a Turkcell nano sim and then load the prepaid sim with 4GB / 8GB of data (depending on how much you want to spend and how good your hotel WIFI is). The issue is getting the sim. Seems near impossible to get them abroad without knowing someone out there.
"Tablets and 3G modems do not require registration" Seems to be a key point here for reusablity if you go back.