You may be aware of the proposed changes to EPC regulations requiring privately rented properties to have and EPC rating of C or better. You can find out more here.
In regards to Knotts Place properties it would appear that the EPC ratings of the top floor flats differ depending on the individual EPC assesors' observations and assumptions. You can check your current EPC rating via The EPC Register website by entering your property address. You will notice the disparity of adjoining properties at Knotts Place. It may be worth taking note of the EPC assessor in each case.
If you own a top floor flat that was re-roofed in 2003 you might like to know that the insulation used was 120mm Thermazone from ICOPAL which achieves 0.18 U-value. This may be worth mentioning to your EPC assessor.