Blocking up solid wall

I've moved into a house with an old first floor external doorway that has been changed into a window. It is half glazed and half upvc panel.
I want to block up the lower half and fit a new upvc window above.
I believe the wall is solid stone construction.

Would it be a straight forward job of using blocks to build this up to the required height?
Would I need to 'tie' the blocks into the existing wall using masonry nails or even a wall starter?
Is permission/regs usually needed for reducing an opening size?

As you can probably tell I'm no brickie but will get someone to match in the exterbal render.

Cheers

First floor external doorway? Was it a fire exit?
Anyway, unless the place is listed or in a conservation area then crack on. Always a good idea to tie new walls to existing, starter plates probably overkill, fishtailed frame cramps would be a decent bodge for that job.

Thanks for the reply

It was the old staircase entry but has since been moved due to an extension.

Cheres