But Honda does sell a kit that will switch off the pass. airbag on any pre '06 car as long as the proper government authorization is obtained. This is in Canada and one of our local members is a Honda tech and has actually done this mod. Like I said, the laws of the land will determine whether or not this kit can be installed.
The acquisition of such "permission" and the subsequent installation of said switch will supercede what it says in the owner's manual.
As of a few years ago, the cost of this kit and the installation was around $500.00. It involves nearly gutting the interior to put it in.

 

Weight system in MY06 is there to satisfy FMVSS 208. This is an US law. I don't think UK have them. These systems are not perfect. Don't rely complete on them to make the right decision. I have done enough study to show that u can fool these systems.

The function of these systems are:

Empty : Passenger Airbag Disable Light off and bag off
<6 yr old: Passenger Airbag Disable Light on and bag off
>5 th percentile female: Passenger Airbag Disable Light off and bag on.

 

There's a ton of info in this thread. Enjoy!