Hey,
I'm currently doing my CPL at Stapleford now! For the Nav & Diversion routes, you will fly to all the little grass airstrips around the southeast. Some of them are almost impossible to spot, but the very reason why they make it so hard is so when you come to you CPL test, it'll seem that much easier!!
Maybe I shouldn't tell you this, but whatever, lol - The 170A (The practice CPL flight test) is to Nayland, which is about 3nm north of Colchester, and then you are diverted to Laindon, which is about 10nm west of Southend ATZ.
Hope this helps!!
Mark