Nicely argued on the money front, however...
9x Nimrod MRA4 = £3.5Bn
9x P8 Poseidon = £1.26Bn (currently estimated at US$220M ea or £140M ea at $1.6 to £1)
You do the maths - £2.25Bn saved that would pay for 11,250 nurses over 10 years or 9,000 school teachers over a similar period.
When the cost differential between COTS and "buying British" is so stark then your argument doesn't really cut it for me.
LJ