...new fog lamps and centre caps? ...ebay...scrap yard...might take some searching though 
Does sound like she's using a lot of fuel...I'm sure you should get closer to 300?... there are lots of MPG threads you could check for more info/comparisons
http://www.micra.org.uk/threads/mpg.54670/#post-565054
...not sure about more technical stuff (speedo...throttle bodies) but I'm sure someone *cough* Frank or Polly *cough* may know 
ETA: welcome...By the way 