I think the price was good for such a low mileage. There's not a BIG improvement in later bikes and actually I think that the earlier ones (around '02) look better. On Yer Bike, who sell at low prices, but give service to match, has new Ballabios for £5,399 and 02/03 V.11 / LeMans for £4,499 - £4,999.
If you look, there are usually plenty of these bikes for sale. As Baldini says, keep looking at MCN, but you should also find them easy enough on the web. You should have no bother finding one and it's worth considering the silver one again. If it's a dealer then you should have some guarantee / come-back.
There's a lovely early green one for sale here, but the dealer still wants £6,400 for it – which is absolutely barking.
I've been wondering why so many second-hand Grisos are coming onto the market so soon?