Welcome Chucter,
Again I'd say your 10k time is also due an improvement based on the 5k time.
However, I reckon you may just want to add a bit more distance to your interval lengths and your long run.
For the intervals you may want to try either reducing the rest period/adding some reps to your 400 sessions gradually or try something like 4 x 800m/1,000m with 90seconds rest. This should get you used to running further at quicker than race pace.
Also, adding a couple of miles to your long runs would be useful maybe up to 12.
Your tempo run seems very tough based on a 42:30pb. I'd say if you can manage 9/10k at 4:10/km then you are pretty much in sub 40 minute 10k shape. If it's comfortable enough and not hindering your other sessions then keep it up until your 10k. Otherwise, you may want to slow it down a bit.
Lou, that's simple, tell Ms D that YOU have a 5k planned!
I don't know what it is about km/miles either as I was orignially a km man and have recently converted.