Imo adding O2 spacers to the Berks will be a waste of time with the only real way to fix the problem being having an UpRev.
If you can't afford the UpRev rather than buying the spacers a better use of your money would be to get an OBDII reader so you can read any error codes, reassuring you that when the EML does come on it is only because of the O2 sensors & nothing else, ...it will also make switching the EML off a doddle.