Paul,
Mine is an 06 which I had new and has now dine 118,000 miles.
1.6 petrol averages 40.3 miles to the gallon, according to trip computer.
I have been trying to think of things to look out for but over the last four years all I have had done is replace brake pads, tyres, part of the exhaust and had it serviced.
As mentioned earlier, everyone will have a laugh at your expense but usually they come round when they discover how easy these things are and how practical.
Servicing at Citroen dealers is on a fixed price menu and reasonable but after mine I was out of warranty I use a local independant garage.
It's always started. runs well, so sorry I can't advise you on faults to look out for.