[Talk-GB] Payment required, but online only, for unattended venues

[Chris Hodges]

Similarly to my other question, the Loch Lomond wild camping spots 
require a permit to be bought online in advance, thus there is a fee 
(with spot-check enforcement, so it relies on honesty). But the values 
for the "payment" key all apply to paying at the venue (per the wiki), 
so how should I tag this?  While credit cards are obviously used for 
this online payment, saying they're accepted would seem incorrect, and 
payment=online would seem like a useful tag.