Paul,
There will be multiple codes for the 233s because they come in several colours. Check the individual listings before ordering. If in doubt, write to Gil at Better Car Lighting using their "enquiries" email address for advice. Refer to my order if you like (Jim Hepburn) and say you want the same thing. I ordered the wrong bulbs initially and he took them back and sent the correct ones. He even offered to exchange them again if I wanted a different colour. Very good service.
The LED bulbs are bayonet style and look too big for the sockets in comparison to the originals but they fit fine.
You'll need 7 bulbs - one for each of the central gauges and two each for the speedo and tach. Order a set of 8 for a better deal and, of course, you'll then have a spare bulb.
Note also that the brightness of the LEDs will overwhelm the green tinted plastic in the sockets so the instruments will appear white. If you want the original colour, order green 233s.
The upper sockets in the speedo and tach are a sod to get to, especially the speedo. I ended up disconnecting the speedo drive to get access and even then be prepared for scraped hands and some swearing. Watch out you don't end up fitting a bulb in an indicator, parking brake or main beam socket, too.
Good luck.
Jim