There has been no one return here to post, that has actually defaulted on an international timeshare maintenance fee obligation.
Most contracts have a venue clause that allows the creditor to litigate at the least possible cost to them. That being said the judgment obtained is only enforceable against assets located in the jurisdiction that issued the judgment. {The Specific State}
Reporting the debt to one of the three US credit bureaus can impact the debtors ability to obtain or the rate of future financing and does sometimes compel a debtor to settle the bill.
I am not aware of anyway for a US judgment or debt to end up on a UK credit report.
Since you are located outside of the contract venue, the debtor would need to then apply to a court in your jurisdiction (the same legal theory applies to US citizens, an out of state judgment is called a 'foreign' judgment) to confirm the judgment, before they can take action to enforce the judgment.
http://www.ccaacollect.com/images/enforcing.pdf
Although, all of the costs associated with collecting a debt,get added to your debt, the creditor will generally not incur those expenses, unless he has knowledge of assets that can be attached to satisfy the original obligation and the additional out of pocket costs incurred.
Rather than rely on a US based message board of active timeshare owners asking advice on defaulting on a US Contract obligation, you should get the advice of a solicitor familiar with the actual impact of walking away from a US contract.
https://www.gov.uk/legal-aid/what-youll-get
If you have a moral issue with defaulting (the cost of default was built into the purchase price and continues to be budgeted for in the ongoing maintenance fees) Then you should try to give it away which might cost you additional funds in prepaying maintenance fees. If you do take the give it away route, be sure to use one of the closing companies recommended to make sure both the deed recording
and resort transfer is completed.