It's good to hear that P6s are becoming more widely appreciated, though I fear as prices begin to rise like this, there is a danger of an increasing number of them being treated like ornaments, rather than being used as intended. I'd love a series 1 3500, but given the way that prices are going, it won't happen for a very long time.
Could it be that P6 prices are beginning to fall into line with those of P5s/P5Bs? Certainly P5B prices have really come down in the last 18 months or so, as it's not that long since there were lots of lovely ones for sale for over £10k, but now you can own a lovely one for around £8000. I imagine that 2000s may eventually reach 3 litre prices, but I imagine that, as ever, they will come second to V8s in terms of values, which isn't necessarily a bad thing, as it means that parts remain affordable for 2000s.