Searched the forum; couldn't find an answer... I'm thinking of traveling Glasgow to Euston this September using a 1cl Britrail Pass. When checking the Sleepr.scot site a few days ago, I thought I saw the 1cl berth supplement as 50 Pounds. Checking today for that same route/date, the supplement is 75 Pounds. Are the berth supplements dynamically priced? Checking that same website, it appears that sleeper supplements for travel before 5 or 6 September are priced at 50 Pounds; but rise to 75 Pounds for the various random dates that I checked after the 6th. Also do they fill up the 1cl coaches from Coach J, K and L (in that order) or from L, K and J? Any insights to these two questions? Thanks in advance.