The Dalmatian coastline and islands around Dubrovnik look stunning and a great area for exploring beaches, town squares, national parks, nature, wildlife. Seems to be something to suit everyone with crystal clear waters, beaches, lakes waterfalls. Ideal for walking, chilling out, people watching, shopping, boat trips etc
It won't be quite so busy in September. May have to stay just outside Dubrovnik, depending on the cost of accommodation, but flights from UK seem reasonable. Would like a trip of about 12 days and looking for like-minded people who'd enjoy the same, just a small group of maybe 4. Exploring in the day, and finding a good restaurant for al-fresco dining in the evening, maybe some live music if available.
Have a look at the video for an idea of what the area has to offer.