Ron,
The unit price of Tranche 1 was £45.45 m (excluding R&D, production investment, etc.) and of Tranche 2 it's £42 m. Those are official, audited figures.
The last proper NAO average UPC was £49.1 m in Major Projects Report 2004, though it included production investment costs and some weapons system costs, and so was higher than equivalent US UPCs, which don't.
The last NAO UPC (in major projects report 2005) was given as £64.8 m, and the MoD have said that these included fixed costs from all three Tranches, but that these are now divided by the total number of aircraft in Tranche 1 and Tranche 2 only, making them an inaccurate average.
NB: The MPR 05 figure is some £20 m higher than ALL other available Typhoon figures. It's £15.7 m higher than the previous year's figure. There has been no increase in costs to account for that, only a change in the way in which the figures were drawn up. Eurofighter GmbH's Programme Director has challenged the £64.8 m figure in print.
I suspect that a full explanation will appear in print soon enough.