Furthermore, we are not particularly attached to the stone.

I’m a bit confused about the stone and brick walls. Is it all original? is the stone walls real? personally I’d render all the bricks, paint the windows a softer colour to tie in with the stone walls, including the windowsills externally which should be painted to match the render with both at the dark end of the stone colour range. The verandah stone doesn’t match anything and should go. But if you don’t like the stone...

I'd replace the roof and brick (paint/render) and. keep the stone

It looks like a 60s classic. I would try to enhance its features not render over or disguise them.

I'm trying to work out what angle pic 2 is ? It doesn't seem to tie in with the roofline and fencing in pic 1 ?

Anyway , I quite like the front ( I assume ) in pic 1 . I'm not a fan of the stone , but I think the brick adds to the fun factor , and the 2 together look better than pic 2 , which is mainly stone . The windows are okay IMO -- if they had still been grey aluminium I'd say get rid of them , but the powdercoating , especially with your coastal location , is as good as it gets in that era .

If you convert the garage to 2 bedrooms , do large white windows the same , probably with charcoal timber in-fill , same as the existing garage door .

Waterblast the roof , paint that veranda or whatever it is in Pic 2 the same brown tone as your tiles , and maybe its just me , but I'd try and remove that white pole thats right in the middle of the lounge window view . It's not too bad , but it certainly grates me . If you can't remove , maybe a sandy beige to match the stone ? Not white anyway .

And if Pic 2 is the rear , I hate rendering , but I'd try and paint ( or render or even use composite over-panels if all else fails ) those brick infills , in a charcoal , to match the front .