We had a 206 1.4hdi for 6 years, would be a tremendous first car. £30 a year tax and easy 65mpg.
Very good safety rating for an older car and should see a few within the budget you have, also most have very good spec (aircon, power steering etc)
Driver seat should have height adjustment, if not then gti half leathers go for nothing these days.
Would personally avoid 106/saxo as they crumple too easily in a crash.