Hey, completing the set IS important. I have seen many S1s which are being priced 5-6 times what a S2-3 in the same condition would fetch.
Well , if you need one to complete the set then you have pay current market prices . If you wait a year or two you might get one for less than they are going for now . It is quite possible that the bubble will burst , in this country , if the economy takes a downturn and the rich people who are driving the prices up put their money into other investment opportunities .
I suspect that Series One prices command higher prices because they don't look like every other Series and Defender Land Rover that has been built since 1958 , and their perceived rarity value .
Do you want one that requires restoration or one that is already restored ? What's your budget ?