I don't think I am.
If one was to take a survey of all the semi-pro and pro musicians in the UK, I believe you would find that most work within their own immediate area. I say that from the knowledge I gained from when I started gigging in Liverprool in 1969, right up to where I am now (and will pick up gigging again in January, Covid permitting). At any given time, there is not a whole slew of bands in every city throughout the UK touring the continent.
But it is an interesting discussion, and one of the many issues that has cropped up, but as I said the carnet scenario is one that has been in existence for as long as the CITES laws have existed, and that is the failsafe way to ensure an instrument is not confiscated, and potentially destroyed by the authorites. It's nothing new, and has nothing to do with Brexit.
Gibson got done by the US authorities under CITES several years ago for falsifying documents relating to the importation of wood in order to bypass the CITES regulations. Look it up, it's all on t'internet.