There are increasingly more childminders like myself who specialise in after-school and holidays for school-aged children. As a result, I believe you are being realistic to think you can find someone to do after school pick-ups.
When I first started out, many people said that I would have little interest because of the after-school clubs. "No one will come to you because they will have their children at the school's club" I was told.
They could not have been be more wrong. It turns out that many parents (and children) are very unhappy with the after-school club, and would rather have their children with a childminder. More importantly, the children would rather be with me at my home!
Also, unlike the staff of an after-school club who will be keen to get back home ASAP after closing time, the advantage of a childminder is that they are already at home. Childminders like myself are at lot more flexible (within reason) regarding collection times. If you do not pick up your child at 5.30pm on the dot, a childminder is unlikely to complain so long as you phone up to forwarn them that, for example, you are stuck in traffic and are running late.
Your best bet is to contact your Families Information Service where childminders like myself will be registered.
I'm new to childminding, so I am only just learning the ropes. However, reading through some of the other threads, I am at what some childminders do. For example, expecting mindees to sit and watch the childminder's child at their weekly after-school judo/dance/gym lesson. Or accompanying the childminder to their child's doctor appointments. In my opinion that is appalling practice.
As a result, I would ask the childminder what type of activities your child will be undertaking in their care.
As part of my marketing course, I wrote (with enormous help from the Bromley Childminding Association - so many thanks to them!) a portfolio document, a bit like a school's prospectus. I provide a copy to all parents who sign up. My portfolio contains all the policies, procedures, activites, schedules/timetable, etc and equipment available to use.
Perhaps that's something you could consider? Either way, good luck with your search!