A lot are over priced to be honest, however there are some that offer the whole package, equipment the lot. I bought my kit from a very successful oven cleaner who mentored me through the process..
Taking the oven to bits and putting it back together is where the fun starts, and my biggest tip is, take a picture of the numptys if they are numbered or make sure you put them back in the right place.... This is very embarrassing when you get it wrong

It's a disgusting job but seriously satisfying when your're left with a gleaming oven and an overwhelmed customer!