I've had a nightmare of a day trying to fit a new downpipe and I've rounded off my post cat o2 sensor. I'm looking to get a replacement ASAP. can anyone recommend a good, cheap and quick delivery sensor?

 

Good and cheap don't normally go hand in hand unfortunately. As they say, buy cheap buy twice.

For lambda O2 sensors it's always best to get a genuine Denso one otherwise it will just fail again after a short period of time.

I've always found the cheapest place to buy genuine Lanbda sensors is a site called sparkplugs.co.uk

 

+100 for OE Spec DENSO.

 

+101 for Denso,
I have used these in the past.
World Car Parts

 

Nothing wrong with a Bosch equivalent IMO, assuming you can find one with the right wiring (or re-solder the connectors to fit).