What is the best (mix of cost effectiveness + speed) way of getting to London's various airports?
I'm an American that will be staying extremely close to St Pancras station for a couple weeks. It would be nice if there was a convenient way of getting to the various airports so I could take day trips to other cities in the UK. I see I can buy tickets online to get from St Pancras to basically every airport, but I'm not sure if it's the best way. Most do look pretty affordable, but I'm unfamiliar with the speed and reliability of the trains.
For example, I've been to Japan several times and they have a rail pass for visitors that works on the largest rail system (JR). I doubt London has any equivalent, but maybe? Or maybe there are day passes for use on certain trains that could get to me the various airports?