I became a single mum of two working full-time in a demanding professional job with no help from family at all. I only had two and that was very tough but looking back, I'm so glad I did it. My kids are now 16 and 13 and they've grown to be independent, hard-working and ambitious and I do feel that seeing me doing it all has had a massive influence on them.
The way I did it is firstly by putting a lot of effort in my work and working relationship so that my bosses could see that I wasn't just working for the money but cared about the organisation's success and was an integrated part of the team. That meant that I gave more than I had to and in returned, I earnt their esteem and therefore their flexible attitude. They knew that if I asked to work from home one day because one was ill that I really was working from home and that I really would finish my project, even if it meant still working at it at midnight.
I also quickly built relationships with other professional mums at their school/nursery and approached them myself about sharing childcare. I hated being the one doing it, I don't find it naturally to ask help, or even suggest it, but once I did it once, and it was so well received, I was very relieved. We ended up in a group of three mums with children of the same age, and we arranged the whole summer months to fit around us. Sometimes we had 7 kids each to look after, but in a way, it was easier as they entertained each other. They were all well behaved kids who were friends with each other, so there were never any problem. As a result, I managed to avoid the worse of childcare costs, with only needing 4 or 5 days of holiday club. Organising it all was quite a task but well worth it.
Finally, I ran everything military like and empowered my kids to take on responsibility. They quickly learnt that they were responsible for sorting out their school bags, making sure that anything needing signing was handed over, took control of their homework and came to me for help if they needed it instead of me asking them.
And finally, I gave myself a break when sometimes it all go too much and felt exhausted. Yes at times I have shouted at my kids because they were pushing my buttons, and I did at times neglected having a perfectly clean house and well tendered garden. I also made the best of the times my kids were with their dad and didn't feel guilty that it was a relief that they were away for a few days.
The reality is that there are many professional single mums working full-time and we all share some characteristics, we are always knackered but have selfless, confident and well adjusted happy children so we can't be doing too badly and of course, it does get easier. Mine are now teenagers and no trouble at all. Good luck.