|This is quite common to see bricks suffering from old age (and occasionally poor pointing)|
This is the type of wall that is commonly rendered over (using cement) because the bricks have lost their faces and hence are much more prone to the weather.
The rendering over can of course cause many more problems due to old bricks (with lime mortar) not being compatible to modern waterproofed cements. The obvious answer, assuming that you are happy to render over, would be to use a compatible lime render. This will work with the wall to help keep it dry and also provide it with the necessary protection from the elements.
What to do though if you want to save the look of your home?
Well, getting the same bricks to match is difficult and would require lots of research as many of the old bricks were made by small local factories that have now succumbed to nationals and multi-nationals. Getting a colour and texture match is therefore a bit tricky.
The answer, though, is staring us in the face (apols for the pun). Each of the damaged bricks will have a perfectly preserved face on its other side, so all we need to do is to turn it around! Easy (said.)
Removing the mortar can be a bit tricky, but where the original lime mortar is, it should be much easier as the mortar is softer than the brick. Where it has been re-pointed using cement the opposite is true and this causes more problems. The use of lime mortar is important for this very reason. Mortar in old houses was there more to keep the bricks / stone apart rather than to stick them all together. When we started building thin walls (cavity walls are effectively two very thin and unstable walls) we needed to stick them together using strong cement mortars and wall ties.
Anyway, back to the point. How to get them out. Well there are a couple of tools that are generally used: Angle Grinders and also Masonry Plunge Saws. The main issue is minimising dust. Silica dust can be nasty and so make sure that you wear a mask. Personally I think that it is worth hiring a Masonry Saw (also known as Wall Saws).
Basically, you then cut around the brick(s) in question and then you can remove them, flip them around and reset it back into the wall using a matching lime mortar. Good luck!