With the new Javascript engine in AE you can now do the following:
First add an angle control to your text layer, then add the following expression to your sourcetext value:
var num = parseFloat(effect("Angle Control")("Angle")); num.toLocaleString("en-GB");
The .toLocaleString option also comes with some other options like percentage signs and different separators depending on the parameters you pass to the function. If you’re interested, I wrote more about these different features in this blog on creating a number counter with commas