Hillbilly you'll love Icmeler!
As for going to Istanbul for a few days, you're better going for a separte break really. It's about a 14 hour bus trip from Icmeler/Marmaris (as you say quite ardous!), you would be better to fly from
Dalaman to Istanbul Ataturk airport, it think the price is approximately £70 each way (could be cheaper though).
Istanbul a fabulous city, I'd recommend you go, I spent a week there one February and would love to go back again, a week just wasn't long enough! You can get really reasonably priced flights out of Heathrow and I think one of the low-cost airlines fly from Luton to Istanbul regularly.
Mazz