Well firstly, even if it is going out of production, you might want to take advantage of that fact and buy it for 136 quid at Amazon (where it is in stock).
As for replacing Diamonds with 902is, depends on whether you have the Diamonds already - I certainly wouldn't be selling them to get 902is instead, the difference wouldn't be big enough. But that said, I prefer the 9.1s anyway - I found the 902 a bit insubstantial (though I know others here rate them higher than the 9.1s, including the staffers, I think). If Richers don't have them, try Superfi, who are quoting £99.
Responsible for the techie bits. Has biased opinions.