Hi Oldtuggo 👋 welcome to the community! Thank you for posting.
Sadly as the community have already advised, you cannot alter the size of subtitles. Sincerest apologies about this!
You can see more about our accessibility support here 👉 Accessibility Services and Products | Virgin Media Help.
Please let us know if there is anything else you need support with. Wishing you all the best! 🌞
Molly