Hiya, and welcome to OSM. It’s good to see you’re enthusiastic about fixing problems in the map, but I’ve had to undo this edit. Changing road classifications is quite a major change to the map, and changing over 100 of them at once makes it impossible for anyone else to check what you’ve done. Road classifications in OSM are not just copied blindly from Ordnance Survey, they’re based on local surveying (e.g. the colour of trunk road signs) and road size and features.

If you’d like to make changes like this in future, please make smaller edits and provide local justification for each change (it doesn’t have to be an essay, but a brief location-specific comment in your changeset message is needed). Otherwise it’s easy to introduce mistakes into the map.

Thanks, happy to answer any questions :)