UK-based ATOs cannot deliver EASA training after January 1st 2021 unless they have a base in EASA-land and apply to EASA to continue to deliver CPL training in the UK
There is the fundamental flaw in your understanding. A base in EASA-land is not required - any training organisation in a third country may apply to EASA for approval as an ATO and there are currently 18 such organisations approved. The major reason that there are so few is probably the bloated bureaucracy of the assessment process and the unknown cost (EASA currently charge a flat rate of €247 per hour with no upper limit). Having been closely involved with one of the 18 aforementioned applications, I vowed never to go near the process again.