Not seen any adders when out running for years. Saw one on the cheviots a few years back and the only one recently was on Cannock Chase. First aider wife says remove as much venom as possible by scraping with a credit card and then get to A&E as soon as poss. You should try not to move as that increases the blood flow and therefore venom around the body. Anaphylaxis is possible too. Not much help in your scenario I know but there you have it. So basically don't stand on one! 😀
Interestingly they are actively looking to encourage snakes and other reptiles back into my local hills so will be interested in further replies.