Managed to get a brand new Lambda for my Mk3 Astra C20NE from my local MotaQuip branch (for local peeps it's near Asda on Newgate Lane). £35 for the sensor and £9 for the wiring adaptor. £51.70 all, I was quite pleased. Though I was gonna pay £70-odd from Auto-Vaux.
Now the car doesn't hesitate, and hopefully the MPG will increase a little.
Just thought I'd share that.