I'D LIKE TO KNOW IF THE FOLLOWING EXPRESSION IS CORRECT: ENGLISH AT YOUR REACH.
why did you entitle the question with "collocation"? :)
ENGLISH AT YOUR REACH is not a standard collocation.
Anyway, the idiom can have a similar meaning as "within one's reach", which may relate to something being close to be grasped, grabbed, tackled, etc.
In your context, English is near to you to be studied, comprehended, ...
Imagine, you browse on the net a lot. On the net there many on-line English courses done via skype and other means of communication, there are many web translators, dictionaries. You can say English is at your reach.