My boots shouldn't be called boots, I'm going to call them foot art I think.
Yangy you are me, except way more heroic. I never went for the distinction between nanny and cleaner (I have also never lived in the UK with kids, and have never lived in cultures where dedicated nannies exist, so it wasn't particularly a choice). I've always had 'nannies' who also clean and cook, and the kids except dc1 have spent part of the day at nursery when very small. The nanny/housekeepers also lived in and provided evening babysitting.
Now the kids are at school all day (they are in French school so go all day from the september of the calendar year they turn 3 - so it was from 2.9 for my dc2) I have been making do recently with a variety of alternatives. One is having evening babysitters who also clean and iron, so much more for your money. This is completely normal here - not sure whether such a thing is on offer in UK. We've now got an au pair, which I find a lot of investment of money and emotional energy for a somewhat limited return, but it is pretty inexpensive for flexible childcare (covering all impromptu business trips, care for sick children etc), and she'll happily run errands, sign for outnet deliveries and suchlike important tasks. She also walks the dog every day. And I like her and so do the boys. I'm looking for a permanent cleaner/housekeeper as well at the moment, in addition to au pair, for 4hrs/day to do all the chores and cook dinner.
I spelt all that out to show that I require way more help than you have just to keep afloat, so you should recognise that you're doing a lot and it's not surprising you're exhausted. Despite all the help I still find it totally unsatisfactory because I don't personally spend enough time with my children. My colleagues all work until 8pm too. I now work 75% from home as it's the only way to see the children day to day.