I very much agree that Mrs Marlow especially is a spender not saver, but I do wonder how much they could realistically have been saving out of Commander Marlow's pay. (I suspect the background problem here is that Forest hasn't really thought about how to reconcile him being a naval officer who will naturally send his children to boarding school, and that there are eight of these children.) I have been trying to work out how much he would have been paid, but it's tricky - there was a marriage allowance, and something for children, but I can't find the exact figures for that. His basic pay before allowances would have been about £850 a year when at sea. When they originally married, as a lieutenant I think he would have been getting about £400-500 a year when at sea, a bit less in a shore job (depending on exactly when we think they got married,a of course). Perhaps Nick and Lawrie at home being delicate (& with corresponding medical fees) may not have cost much less than when they are at school.

Of course, they probably should save the legacy, if nothing else - otoh, I have some sympathy with wanting to stay in a hotel in 1947 or thereabouts, and food and rationing being someone else's problem for a while!