It will be treated as a purchase.

Also, if the person in the UK is receiving it as British Pounds ( instead of US Dollars ), enter the amount to be send as GBP , and make sure to select having the currency conversion done by your Credit card ( not PayPal ) as Paypal's rate is worse.

Right below Payment Method, you will see "Other Conversation Options" and select Bill me in the currency listed on the seller's invoice.

Use only cards with 0% FTF though, like the Ink Plus or Sapphire Preferred.

Finally, if it doesn't have to be funded by credit card, consider using XE.com to send the money.
They are a currency trading platform and have competitive rates and lower fees.