That craft is not a BBV 3 , it's a smaller craft that was modified with a lift engine, I've forgotten what BBV called it but I remember some YouTube video a few years back. I spoke to Bill about it several years ago.
Essentially a BBV 1 with a lift engine if I remember correctly. They were very quiet for the time, but only about 3 were made. The good news is that it's a pretty good craft. The bad news is that you've been poorly advised with the bonnet.
When I first saw the photos, I wondered how the lift air could get in through that tiny inlet. And it seems it can't! Possibly compounded by (if I remember correctly) a quite small lift engine, because they were intended to be able to race in F35 I think? The idea that it was possible to make a racer-cruiser was always flawed, but the BBV1/lift engine craft did make a half reasonable cruiser. There's some footage on utube somewhere of two of them on the Wye and Severn at one of the Berkeley treasure hunts.
So first thing, take the bonnet off and see whether that makes a difference. And let us know what the lift engine is.
Ian