Looks like you've got a good deal to be honest, the 1.4's hold their value a little bit better than most of the other models so £500 is quite good.
Here's a little buyers guide video i did that might help you with some of the common problems that the Micra's have
[MEDIA=youtube]8ATVhi-jCQ8:36[/MEDIA]
Also Fiesta wheel won't fit the Micra, the Micra has a 4x100 stud pattern and the Fiesta has 4x108
