Your layout may have been compliant before the loft extension. However adding the loft extension means different things apply due to the height and distance of escape.
So, if the height of the finished floor level of the extension is less that 4.5m above external ground level escape can be provided either by a window (min sizes and max height applies) or by a protected stairway.
If your floor level is above 4.5m then jumping out the window isnt an option so you’ll need a protected stairway.
Need more info just ask. I can send you the regs or find a link if required