I still can't understand why you have a problem or think this is about the Electoral Office being lazy.
The Electoral Commission demands a national annual survey to be carried out in the autumn. There is a national cut-off date of 15th Oct, with the result to be published by 1st December. In order to process the huge amount of data, councils issue the registration form in August on the basis that most people know who will be living in their property in three months time because for the vast majority of properties this will not change, and this gives them plenty of time to process the information.
For the very few people who are unable to determine much in advance those living in their property on 15th October, the system also provides plenty of time to capture these details and ensure they are processed within the timescale.
Evidentally there are a few people who go out of their way to be deliberately unreasonable too, and the system allows time to ensure that even stoppy gits get the right to vote.