I am flying with BA from Heathrow to Vienna on 10th September at 12.40pm. I am staying in Vienna at the Terminus hotel (from Booking.com) two nights then getting a train to Bratislava after check out on 12th Sept. I will be based in Bratislava until 15th (staying in a central AirBnB), spending at least one full day in Bratislava and may do day trips elsewhere. After check out on 15th Sept I will get a train back to Vienna where I fly back to Heathrow on BA at 7pm. Feel free to join just for the Vienna stay or just the Bratislava stay or all of it.
I tend to explore all day (mostly by foot) and then go to a restaurant in the evening. I don't go clubbing but you are welcome to do so, you are welcome to join me for some or all of your time there.
You will have to sort out your own flight and accommodation but perhaps if there are a few of you interested then you get could get an AirBnB together.