Yes, it is a big step up. You go from being capable of "limited and simple" job scope, to being the man on the spot when decisions need to be made, and your years of experience pay off under these circumstances. Get the A Licence under your belt and working it. Get used to having a limited amount of responsibility. Get involved in defects and operations. Learn the trade with a bit of depth, and then go for the rest of the B1 modules. The stuff you will learn in the meantime will help with the exams and be useful in the future. Bear in mind the minimum age requirements in the regs as well - 18yrs old to hold a licence, but 21 to certify under it. It is experience that will make you a good LAE, not exams.
Oh......and Airmech is pretty dead these days unless you want football results!