What is the difference between Anglia and England?

What is the difference between Anglia and England? When it's used.

Some examples of modern usages:

• probably coincident, but Anglia in Polish language is England,
• there are regions called East Anglia, Mid Anglia and West Anglia,
• there are schools such as Anglia Ruskin University in Cambridge, The College of West Anglia, Anglia Ruskin Students' Union,
• Anglian Water in the UK, Anglian Bus,
• Greater Anglia trains and Anglia Railways,
• and similar

Anglia is the Medieval (Latin) name for England and has never been used in my earshot to refer to the country of England (I am English). If it were used now it would imply that the subject of the usage was ancient England.

There is still an area of England known as "East Anglia" in common usage, but there is no common usage of North, West or South Anglia (though I imagine these regions may have local usage of these terms).