Homes to Swap and Exchange in or near Berlin

I am housesitting for two retired teachers in London while on a research trip. They contacted me after I registered as "available tenant" and asked me to look after their house and cat while they are traveling. It has proven a wonderful solution so far - maybe this is exceptional as they were clearly more concerned about finding someone nice and reliable than about the rent. I flew over to meet them beforehand as I'm going to stay on when they return for another month (so wanted to make sure we got on well). I think your SabbaticalHomes.com is really really good, it was recommended to me by an American colleague who has also successfully used it.