Through Thomas Cook for example (used to work for them) if you wanted to change your accommodation but still go on the same day and flight then it would cost GBP25.00 or GBP30.00 per person when your departure date was so far in advance.
And I wouldn't have recommended Playa Paraiso to 4 adults! Did they ask you what type of resort you wanted (lively, quiet etc)? I will be staying quite near to it myself though, at the Bahia Principe, that's AI and we actually enjoy the fact that were miles out of Playa, but then we do have a child with us!
Good luck and if the worst happens and you have to go, I bet you still have a great time, after all you've got another couple for company, and a taxi should only be about 15 euros between the 4 of you into Playa.
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