I am looking for another car soon with very similar requirements to yours, the cars I have in mind are:
EP91 Starlet- Cheap to buy, plenty around (both on the road and in wreckers), toyota reliability, fuel efficient (probably around 6L/100kms), simple, timing belt, 1.3ltr
K11 Micra - Cheap to buy but not many around (forsale and in wreckers), reliabe, fuel efficient (around 5.5-6L/100kms), timing chain, 1.3ltr
AE92/AE101 corolla - Even cheaper than the above, they are everywhere, reliable, fuel efficient (around 7L/100kms), timing belt, 1.6ltr (I used to have an AE92 daily and it was great)
Early (1999-2001) Echo - Getting newer, has some newer technology but still simple, reliable, fuel efficient (around 5.5-6L/100kms) timing chain, 1.3ltr (My mother has one of these and at first its pretty ugly but some tint and wheels fixes that, dunno if its just hers but has a huge flat spot of no power in the low revs of second gear)