Apologies, don't mean to cause offence & didn't realise the bass was owned by a BC member.
However.
I do know a little about Japanese instruments from this era, and having (a few years ago now, admittedly) bought & sold them to earn a living, I do have some awareness of the market for them, and their values. The simple fact is that, like any vintage instrument, original components and finish, both in good order, are paramount to their value. Refinishes and non-original components (regardless of quality) are unlikely to add value.
I can only look at an instrument from the perspective of what I'd expect it to achieve if I were selling it - and a VA900B in top condition would likely be a £350-£400 bass. They are excellent instruments but looking at Matsumoku builds from this era, the Vantage brand is valued a bit lower than similarly specced Westones, and both of those are poor relations to Aria Pro SBs & SB-Rs.
Of course these are little more than assumptions on my part & I'd actually like to be proven wrong about your bass. I hope you get your asking price.
Just in case you are interested. I have had someone offer me the full asking price so it just goes to show if the right buyer comes along...