We always go for around 4 to 5 weeks from mid May until around 15th June. May/early June is lovely, long light nights, everything is fresh and new and the weather is not too hot. This is our favourtie time and we have been coming out in May/June for around 10 years now.
We then come back in September for another 4 to 5 weeks until October. This year through a set of circumstances we came late in September and stayed until late October, we were so lucky as the weather was lovely and warm, no rain. However, the one disadvantage for us was the short days of daylight.