As mentioned by T_Bacon, Mapinfo has an import functionality for OS data.
• The .gz files are a type of zip file (I did not know that as they were just identified as .files on my laptop) – unzip them provides a GML of each tile.
• Each tile is then individually loaded into Mapinfo (v16) using Table -> Open -> Import -> Change file type to OS MasterMap (gml) – this breaks down each GML file into its constituent pieces with the relevant OS symbology (as close as Mapinfo can get it).
• Then you create a new table for each constituent (topo area, line, point etc) – the 8 tilesets are then appended to that table. This is so we only have 1 file to load for each part, as opposed to 8 (a quality of life improvement).
For QGIS, I set up a postgres/postgis server (make sure to enable to postgis extension or you will receive errors), and just loaded the .gz folders into OS Translator. Took about 5 minutes to merge 8 tilesets and apply to symbology - far quicker than Mapinfo but there is not way to transfer symbology between QGIS and Mapinfo. If you use ArcGIS and QGIS, you can keep symbology between both applications by saving a layer file with the .shp files.