yes from what I've read it seemed there was a lot more Bohemian glass and some French glass coming this way than going back the other during that period. But again, that's just my impression. I don't have tonnage of imports to back up that surmise, though I think they do exist. My impression from my readings over time is that it was a hay-day period for Bohemian glass and their exports (not pressed glass though). Pressed glass seemed to be in ascendancy from Baccarat and Saint-Louis.
I wondered when doing all my reading, whether the Hale Thomson patent was done because the technique was good for use on mirrors for example (that method was much more healthy as the previous method was poisoning the workers) and Belgium and France, where they registered their patent, was a big supplier/maker of mirrored glass. From reading the court reports on their case, it seemed they didn't have a problem popping across the channel to register their patent. There was no indication it was a difficulty. Also prior to 1850 they were using Bohemian glass and silvering the interiors and again there seemed to be no problem with supply.
I think glass trade into England during that time (early 1800s to 1850)was big. And part of that was possibly due to more attractive colour developments (certainly with Bohemian glass) but possibly also English development of coloured glass was restricted by the prohibitive tax up to the 1840s.
In the case of the Hale Thomson patented silvered glass there were lots of developments in that time for the use of mirrored glass for telescopes for example, so presumably they also wanted to register their patent to protect for a potential growth in that market.