How much is the discount for the Eurostar when you already hold a Britrail pass? We found a 20% discount online, but wondered if the discount is more than that in person at St. Pancras station.
Well I don't know where this 20% discount came from but great if you can get it. Can't imagine (after looking at the web) that you'd do better in person. That said buying your tickets in advance, on-line, non-refundable is what $57 each way. No hassle, no worries...
In my experience, the discount for a rail pass is very minimal. Getting the discounts for buying well in advance is much better. Buying in person at the station you will pay full price. The Eurostar works much like airlines, cheapest seats are sold well in advance and last minute seats are full price.