There have been significant changes to Part B of the Building Regulations.
The 1700mm rule was a maximum and whilst not cited within the Regs, compliance with the min/max height of the window cill is applicable. The escape window will still apply as it will form part of the overall escape strategy.
More importantly though is the means of escape from the upper floors through protected routes to a safe exit at ground floor level. We trust that you have considered these aspects within your design as well.
