I've got an end of July "baby" and had the same concerns. Still do, even though she's now in Year 1, if I'm honest! But, knowing what I know now, there is no way that I would turn back time and skip the Reception year. It really is a great bridge between nursery and the "proper" schooling that starts in Year 1. Due to not getting into the school we wanted initially, my daughter missed most of the first month of Reception as we waited for a place, which meant that she went straight into full days, 5 days a week. No settling in for her! And she coped much, much better than I thought she would. I struggled more than she did!
To be honest, all the younger children in the year seem to have taken to school with real enthusiasm. There is a massive difference both physically and developmentally between the oldest and the youngest at that age (which is to be expected because it's a 20% difference in age when you think about it!), but there is also a big difference between maturity levels of the July/August children who are now in Year 1, and the September/October borns in Reception.
Don't worry. I know it's easier said than done, but although it's terrifying sending your just-turned-4yo into a classroom, they love it! My only word of warning is that it is a big jump from Reception to Year 1, so be prepared to give lots of support during that transition. Again, the young ones seem to have taken it in their stride at our school, but some children do find the move to more formal learning a bit difficult.
Your little one will surprise you, I can virtually guarantee it