I have a female cat who is out in the garden all the time.
I also have weeds along the brickwork at the bottom of my house, as
well as in the garden itself.

Could you please give me some advise as to what weed killer would be
suitable to use and would be safe if you have animals like cats &
dogs.

If they are in places that you don't want ANYTHING to grow, like
between sidewalk cracks, or between patio bricks, you can use a strong
salt water soultion.