Interview went really well - I gave it my best shot, and I liked all the people a lot, particularly the guy I would be working for. I hear early next week if I have got through to the next round.
WFH, anything is possible with a willing and supportive DH and a good nanny, but it is true that they need you more when they are at school because schools don't offer the same level of holistic care as nurseries etc, unless you go private to one which takes boarders and has a san, homework clubs and so on that younger day pupils can use as well.
But it sounds to me like you are not ready for this. However you could find out more about how much notice you would get to travel, and how long it would be for each time, plus whether they would meet any additional childcare costs incurred over your nanny's usual f/t hours (which the Inland Revenue seem fine about), or give time off in lieu. You also want to make sure they let you factor in a recovery day if you have been flying long haul, and let you buy fully flexible tickets so that you can hop on an earlier train/plane if possible. If they are RyanAir/EasyJet oriented then it's worth avoiding, as it will do your head in unless it's a quick hop to Scotland.
I find doing a night or two a month is not a problem at all, plus a longer trip of about 5 days, and in fact I love having a bit of time to myself and meeting new people. But we have a rule that we never have both parents out of the country at the same time, and if we are both away from home overnight, we get a grandparent or other relative in to keep the kids and nanny company.
There's a lot to be said for having a live-in nanny if you have to travel. But nannies have lives too, and get ill occasionally, so you do need a back up plan as well.