Ant, I think you have answered your own question really. You know the L322 more intimately than any JLR mechanic, you love the looks of her and how she makes you feel when driving. Your other half also loves the model. It is a nice roomy space for all of you and more practical for a growing , young, family, than a 110. As the kids get older you/OH might want another 110 but right now , it's not the answer , nor is any other vehicle that will leave you wishing you'd got a Range Rover.
You could opt for a P38 but you would still hanker after the L322. So a year or so down the line, you would be back , with a similar post.
There is another thread, running concurrent with this one, where someone else is also asking should they or shouldnt they. The difference is the humourless naysayers haven't waded in, with undermining comments, because of the situation the member finds himself in and they know they would get torn apart.The reason I mention It is because it highlights one thing very clearly, life is too short for regrets. Take your pleasures where and when you can, you never know when circumstances might change.
In summary, I still say go for it, you know you want to