Traditional "brown TV coax with copper braid" is virtually useless for Freeview signals. Analogue TV signals were very tolerant to interference - remember those pictures which were more snow than picture?? - but digital is much more sensitive.
Traditional TV coax is useless because the braid is so open it lets all sorts of interference through.
Use satellite grade coax with a braid AND a solid metal foil sheath.
The coax cables from the TV aerial point to the Humax and from there to the TV are just flexible TV signal cables, don't know how well they're shielded. Are you suggesting I use solid core coax instead of the one's I just mentioned?