Loft hatch replacement

[Tigercubrider]

1950's house.
Current loft hatch seems to be T&G boards covered on the ceiling side with thinnish (9mm?) ply. Hinges down to allow a loft ladder. Currently no insulation

The current hatch is draughty despite a bad attempt at fixing a fresh jamb around inside. The hatch doesn't seem that square compared to the frame and has some fluff that indicates air movement. The hatch is big due to the ladder fitting.

I think I have the choice of building a new door and frame that's actually square then fitting it to the existing hole? I'd keep any framing but adjust the newer frame with wedges and packers and possibly some new trim?

or

Make a deliberately non square door to fit the hole? MDF? Ply?
I'd use something like kingspan/celotex to insulate it.

what's the easiest? I have access to a reasonable workshop with a wall saw so straight cuts and true square corners isn't an issue.

ta

 

[motorbiking]

Maybe just install some draft excluder and glue some celotex to the back of the existing hatch. ?

 

[Tigercubrider]

would do but it looks crap.
I might see if I can remove the hatch and take off the ply that faces it.
Then I could cut a new piece and replace it so it looks neater.