I work in an oldish town house probably built around 40's/50's. It was refurbished before we moved in, usual plaster board stuff, lick of paint etc. On the wall which joins to next door hund a fire extinguisher which has been knocked off crumbling the plaster board and exposing the brick behind which it was drilled into. It has the look of a light grey powery brick kind of like a breeze block(i doubt it is breeze block due to the age of the property).

How do i know if the brick has asbestos in it?

you wont get asbestos in bricks ..you say the place has been refurbished ..and as a builder it sounds like you have got a thermalite type block wall ..one way you can tell is that they are very easy to drill ...the type of asbestos that is dangerous is the type that was used in pipe lagging ..not normal in a domestic dwelling.....the so called sheets of asbestos sometimes used in garage roofs are normally fibrous cement ..and although they do contain a small amount of asbestos they are not really a hazard...all sheets made after 1987 in the uk contain no asbestos

Brick didn't often have asbestos in it.

If you're really in doubt about whether you have any then call the building inspector from your local council. That's a much better thing to do than relying on people's guesswork.

In the meantime I suggest that you carefully put a single layer of paint over the powdery surface to stop it from spilling dust into the air. Wear a properly fitting mask and do not use a spray gun.

You would have to have it tested, unfortunately you can't tell by looking at it! And taste is for lead paint, it taste sweet, not asbestos you dubba.

100% it has not if it was artex then it could be possible but the amount in it is minimal dont worry about it am a plasterer