Vexillology is a vexatious topic! This is an interesting site:
http://www.flaginstitute.org (well, I think it is!) and supports the assertion that the Union 'Jack' name is a relatively recent arrival.
I like flags and I have a small collection of flags which I enjoy flying on the appropriate occasion. I have just come back from 2 weeks in America and am suffering from flag fatigue as just about every house, shop, construction crane, ex-forces member's grave sports a Stars and Stripes, I like the idea of public buildings and spaces flying a national flag but, for me, less is definitely more and over-liberal use feels more of a reactionary response rather than a sign of national pride.