The red stripes are wrong. The UK flag consists of three flags:

England
Scotland
Ireland

Every flag is shown. The English "+ cross" rules them all and is shown full in the front
The Scottish white cross on blue ground is in the back
The red cross stands for the colours of Ireland, sitting on top of the white cross of Scotland, but is turned anti-clockwise.

So the left side of the flag is wrong, it's just a mirrowed right side.


P.S.: What happened to the welsh dragon?