Thanks for the inputs.

To clarify, if I book the return CW ticket it will be:
40+120+120+40=320 TPs

The MFU is an interesting idea, which I hadn't thought about 'cos of not getting as many points, but with the following maths it does make sense:

I could an MFU, which would be:
20+75+75+20=190 TPs

The full CW ticket will cost 2339 euros, and the MFU will be 1386 euros. So by my simple maths, an additional 953 euros for 130 TPs. If we got an extra 120 TPs by upgrading 3 ET sectors (for both of us travelling on one booking) that would cost:
3 x 125 euros x 2 = 750 euros

Something to think about.....

In total Mr flyingbee needs 350 TPs, and I think we will have 3 trips from France to the UK before the membership year is up to gather additional TPs.

All of this assumes I can get Mr flyingbee to confirm he will be able to have the relevant days off work before all the redemption availability dries up and the fares go up....