Dodgy render - what next?

We bought a house a couple of years back which was re-rendered around ten years ago. Speaking to local builders, they remember the gang who did the job as not being much cop. i.e. the job was done on a price. As far as I can see, it is basically a case of making it good and painting with masonry paint.

As you can see from the pics of the south and west walls, there are unsightly damp patches and a bit of mould. I am guessing they are as a result of the render not being properly waterproofed.

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I have also attached a couple of snaps of cracks in the render. The doesn't seem to be blown around the cracks, but do I need to chase out the cracks or should I fill them.

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The questions I need answered are:
Can I get rid of the damp patches without covering with paint?
If I am just going to apply sealant, what should I use?
Do I need to worry about the cracks?
and if so how can I fix them without spending a fortune?
What paint / sealant should I use?
Is the lack of DPC on these two walls adding to my problems?

Thanking you in advance for your straightforward and cheap to implement suggestions

My guess i that the house was rendered to hide structural defects.
Those cracks are in just the right place to suggest this.

Obviously thats not what I want to hear

The building is old and I would expect there to be some issues with it. But for now I would like to ensure that there is no extra water getting into the structure through the render (I don't even know if that is likely as the cracks are pretty small in my view). Once it is watertight, then I can have a couple of peaceful nights in which to dwell on how to improve the fundamental structure of the building. The half-removed chimney, the breast of which is still present between the ground floor windows on the first picture is probably an issue for a start...

But just out of interest - what structural defects do you think are likely?

There are too many possible answers.. But first try to establish if the walls are actually damp (penetrating damp) by using a moisture meter on both dark and light areas. All render will contain moisture but a difference in the shaded areas will confim penetrating damp.
Render can look like it has damp patches as a result of the render drying out too quickly on application and the dark areas can appear when it has been overworked trying to get a good float finish. If it is damp and you want to seal it you will have to install a DPC where there isn't one beforehand or any rising damp will be forced onto internal walls.

Haveing no damp course will only effect walls lower than 1 metre from floor level. Install one anyway, you can do it yourself with "dryzone" or get a good outfit in.

I wouldn't worry too much about the cracks, especially if the render around it is sound, a house this old is going to have some movement and it doesn't take much to put a crack in render. These days fibres are used in the mix to help prevent this.

I've not seen it but heard of a breathable exterior paint. If lime was used in the render mix this will help the building breathe so there will be no point sealing with the likes of weathershield.