Hi PLEASE HELP!

1.2 8v punto 2003

misfiring (loss of power) when first start from cold.
feels like its going to cut out and has once or twice.
plugged in and read code for Oxygen Sensor fault (P1170) so fitted new lambda sensor.

in last 2 weeks its had:
2 new coil packs
HT leads
Plugs

also in last month or so I have had Head gasket done, water pump etc...

97000 miles and ready to burn it!

also strong smell of petrol when setting off from cold again! ?