I doubt its just an ECU or restrictor. The 192hp engine has a different part number for the super charger. I would bet there are a fair few differences inside the engine. I also think the 192hp has a different compression ratio. I remember I had a Vectra Di and there was a TDi with an extra 20hp, one difference was they actually had different con rods!!!
So unfortunately I don't think you can get 192 very easily.
AFAIK 3 main differences its different charger, different intercooler and a different map on the ECU best I have seen anyone do on the 163 bhp engine is take it to 178 bhp and then you need to change the compressor pulley or crank puller to spin up the charger faster, would have thought you could not get to 192 bhp without some serious modding and serious pound notes
What year 200k is this.
The S202 C200k that I saw on an X plate was a 2ltr not a 2.3 so surely this would make a difference.
I believe these were the series 'run out' models over here but were normally sold in Portugal and Italy for tax reasons.