Yes that is my understanding. You are restricted by the allowance of what you can import into Turkey. You should then be able to take them into the UK provided you can prove you bought them in Rhodes and paid the duty, but don't shoot the messenger if it goes horribly wrong!
I am basing this on my experience of buying in Madeira on a cruise. We flew to/from Tenerife which only has a 200 allowance. However we were visiting Madeira, which as part of Portugal has a 3200 allowance. When the ship arrived back in Tenerife our luggage was taken from the ship to the airport and was effectively in transit and didn't "enter" Tenerife so we were able to have the allowance of 3200.
I actually called HM Customs and Excise and had them confirm this before I did it and they gave me a reference number of the call in case of any problems. Had we been on a cruise and stay with a week in Tenerife after the cruise we wouldn't have been able to do it.
luci