You will have to assess the cost of aquisition and the long term operating costs, then discover if there are any other ways of meeting the military need.
Many thanks Tinribs you raise a lot of points that will need considering. I think the above quote is very significant and something I want to address in the research. Much of what I have compiled already is data from National Audit Office Major Project Reports (1999-2010). Especially focusing on (forecast and actual) expenditure, ISDs, and slippage numbers as well as other data available.
As well as being long and demanding I hope the research will be enjoyable as well!
Grant.