Front or rear? Not sure if different years or models have a different lay out
front sensor on mine I can see on the exhaust in between engine and radiator, haven’t changed that one but looks like the easier one since it’s literally in front of my eyes
rear sensor down the left side of the engine as you look at it, awkward Git of an angle, blew £30 on extension bars and long socket to beefcake it from above, not enough space to get socket on. Unamused. Ended up pulling all underside trims off driver side too went in through wheel well with adjustable spanner do or die style and cracked it off. Anger is the key.
get one of the offset 22mm o2 sockets, get it from underneath with a ratchet (what I was originally going to do) access would have been a doddle. Mine was TIGHT, try penetrating fluid around the threads if can get near them, anything that helps it at all is a bonus