Relentless organisation is the only way, I think. I was a single working mum to two and it was the only way I survived
Get everything for the morning prepped the night before and I mean absolutely everything. DC clothes, shoes, bags, lunchboxes, coats and all of your stuff too. Have the outfit you will wear in the morning hanging up and ready to go and your shoes, coat, brolly and handbag all out and also ready.
Grocery shop online. Never go grocery shopping it is such an enormous time suck.
Laundry every day, much better to do a small daily load than face a mountain at the weekend.
Make sure you have bin collection dates stuck up in the kitchen somewhere, so they can't be forgotten.
Make sure you have car service & MOT dates in the diary for convenient times. You have longish school holidays to get that kind of thing done, which is handy.
Haircuts, shoe fittings, dental appointments all need to be diarised well in advance and again you have the school holidays which helps for all of that stuff.
All kids school and nursery events need to be noted in the diary as soon as they come in.
Being tidy at home is a massive help. That way you don't lose things unnecessarily and waste time having to find things. Get plastic storage boxes / baskets, pegs, hooks or whatever works for you and make sure that everything has its place. I used to play "toy bedtime" with my two before they went up to bed every night, which involved all the toy crap going back into the storage boxes. It was part of our routine and meant that I didn't come back downstairs after they'd conked out to face toy Armageddon all by myself.
Get the bedtime routine off to an early start every night. I used to get mine bathed and into pjs as soon as possible, so that we weren't all cranky and tired and they could just toddle on upstairs, brush teeth and straight into bed when it was bedtime and all the undressing and getting clothes ready for the next day was already done.
Gifts are another massive time suck, and when your DC are little there are so bloody many to get. Again, order online and have a good stock of cards, that way you don't get caught out.
A slow cooker is a huge boon. I used to sling stew in the pot in the morning and then dinner was sorted when I got home. Also remember that boiled eggs and soldiers with some carrot batons is just fine too!
You have an OH, make sure he is doing his fair share too!