Translation:Would you like tea with milk? Yes.
I don't know the answer to the specific question you have asked, but I suspect that "milk tea" does not exist as a specific identifiable thing in Gaelic, because I don't think it exists as a thing in UK English. I believe (but am happy to be corrected) that "chai" is sometimes used to describe this method of making tea.
Even if you were to describe "tì" as "bainneach" (if that's at all correct) - I think most folk here would only think you meant tea brewed as traditional, but with a lot of milk added.
(One other note, which is intended kindly - you said "outside of England" - please bear in mind the distinctions between England, Scotland, The United Kingdom, and the British Isles.)
Sorry, nothing to do with the original post, but this just brought to mind a story from an Irish friend many years ago (who was learning Scots Gaelic) who had asked an old (Irish speaking) lady about what she thought about Scots Gaelic. Her reply was that it was like: "... tì le bainne na bà nach beò." (well, the irish equivalent anyway!). She meant it was like tea made with condensed milk - milk from a tin - i.e. better than nothing but not much!