I know that students will be able to access their own individual GCSE Maths exam grade from 6am on August 21st but will I, as a Lecturer, be able to access all of my students results from 6am on August 21st using Results Plus, please?

Yes, that's correct. Results go live on the ResultsPlus service at the officially JCQ agreed time of 6am GMT+1 on the relevant day in August. Authorised personnel (Exams officers and Heads of centre) only will continue to receive results a day in advance through the normal channels.