Remux TV Progs to Matroska Video .mkv

[Computing]

Hi, I'm trying to get programmes from the Beeb into .mkv format.

I know you can do it by using --command-tv='ffmpeg -i "<filename>" -c:v 
copy -c:a copy  -y "<dir>/<fileprefix>.mkv"'

but it still downloads the raw .ts file, converts it to a .mp4, tags it, 
then converts to a .mkv as required.

Is there a way to do download  .ts, convert to .mkv, tag .mkv?? I.E. 
Avoid the mp4 lossy conversion??

Thanks loads

Martin