BG, bless 'em, have got a thing about non-barrier pipes. The trouble
is that because they are (erroneously) trusted people tend to think
that using non-barrier will inevitably lead to disaster.
Just to be clear for the OP, even if they are non-barrier there
shouldn't be an issue. They might lead to slightly increased corrosion
in the system but not enough to justify the disruption and additional
expense of removing already installed pipework.