Laurence Payne wrote:

I have noticed this glassiness before, but now I want to do something
about it.

Try to pin down whether it IS happening nearer the centre of the disc.

Very difficult to tell. It becomes more irritating, and one notices it
more after a while, and records also typically get louder towards the
end of a side.

If I recorded it, would that help an expert identify the possible cause?

Could be cartridge alignment (don't tell me a Linn owner isn't
equipped to adjust this? :-)

I assumed that the hi-fi shop I bought it from wold have set it up
correctly, and that it won't have moved around very much since then.

Daniele