By Sachin Ravikumar and Ali Kucukgocmen LONDON/ISTANBUL (Reuters) – Once Marion Parks found out she needed intensive dental work, the 55-year-old decided her best course of action was to leave her small English village to have implants — in Istanbul. Parks is one of thousands of British people going abroad for dentistry. Where once they travelled for cosmetic work to achieve the perfect smile, now many are going for basic dental treatment that they say they cannot get in Britain. “It’s just a sign of the times,” she told Reuters from her home in eastern England, prior to the trip. “It’s a bit …