Go to the appointed place at the appointed time, open your envelope and off you go!
Eventually, you‘ll find out where you are travelling for the weekend. Except for your destination, Pack up +go will give you a list of suggested must- sees at your destination and suggested activities- normally according to the preferences you listed in their survey.
To sum up, they choose your destination, your stay and transport- paid in advance. The only thing that depends on you is how much you are going to spend there.
And, if you wanted to know what will happen if it occurs to you not to like the destination, the answer is that they won’t reimburse for your costs- after all, you were the one who wanted unique adventure!