We have two car seats for sale, both are Safe 'n Sound brand.
One is a Discovery Plus (graphite colour) 8 - 18 kgs for AUS$160
the other is a Hi-Liner SG (sapphire) 14 - 26kgs for AUS$90
(Safe 'n Sound in known as Britax in the UK)
The seats have been owned for three months and have only been used on weekends. They are in really good condition.