HHO conversions in United Kingdom

[martarchitex]

Has anyone tried a conversion in the UK. I am really keen on building one to try on my 1997 BMW 323i which I have had since new so I have a really accurate mile per gallon history in urban and long trips. My car also has the mileage computer built-in so gives the range and fuel consumption for trip or aggregate.
I would like to see an installation in a 3 series BMW (there seems to be plenty of space to fit a HHO generator) but wonder if the O2 sensor for the exhaust and the energy management computer would need special relays.
There seem to be various kit instructions available and various kits for assembly and the prices vary enormously, all with different claims. Some claim a 25% improvement some up to 90%. I know petrol engines have a better improvement than diesel but would like advice on the best self construction instructions. The youtube videos also are not much help as they all discuss the general principles but not whether they have additional safety circuits or the production capacity of the kit on trial.
Any news from someone who has built one in the UK would be gratefully received.
I saw the video of the guy from the Philipines who runs his own designed kit on a multi-valve fuel injected Toyota and he was quoting higher savings on petrol than most of the US sites?

[pdai11]

I have been researching HHO products for six months now and spent over 1000 hours. If you need any help, email me on pdai11@yahoo.com