External door blank

Hello all.

I just after some suggestions for where I might be able to purchase an external door blank (a plain door for a rear fire exit), and an external frame to suit. (it is 2' 6" x 6' 6")

I really need to get it and fit it tomorrow as I have had to temporary secure the existing door tonight.

I know my local magnet trade counter is not open again until new year.

Would this be the sort of thing a builders merchants would carry, or do I need a timber merchants? and are they likely to be open tomorrow?

(I'm in north Leeds if it makes any difference)

Thanks for any ideas

Howdens joinery, Leeds branch?

Are they likely to be open tomorrow?

There website doesn't list and opening times or branch locations