BigWallop may be right, but when you come to sell the house and somebody does notice it, they may try to negotiate a price reduction as a result, or even be scared off. It's one of those issues that can loom large in buyers' minds.
I have a similar problem with two walls. The quality of the construction (1970s) is lamentable - clearly not up to the job long term.
One is right at the front the property in a prominent place and it's a big crack that looks a sight. It has been going a few millimetres a year for the last decade and a bit and is now yawning. I'm sure it would last another 5-10 years before reaching crisis point but our house will be for sale next year and looking like it does and being where it is, it has to be rebuilt. Fortunately that's a short and easy bit of wall to deal with.
The other is at the rear. Half the wall is beginning to tilt forward leaving a small crack but in a far bigger wall (5m *
1.2m), again in a very visible place. This is hardly moving, if at all. I'm in the process of fixing that now. My solution is to build rectangular flower beds in front of it, and the walls of the beds that meet the retaining wall are engineered as best I can to buttress it against further movement. I shall then grout the crack, patch up the render, and repaint the lot.
As others have said, the materials are relatively cheap. It's very laborious work though and you quickly find an alarming pile of spoil developing if you'll be excavating foundations, so price in skip hire. I spent all of yesterday concreting. All the day before excavating. Today I'm doing nowt becuase I ache!
Reclaiming bricks/blocks takes yonks. An SDS drill with rotation stop and a 40mm chisel makes it far easier. Even then you may feel that the price of new ones (and the skip to take the old ones) would have been worth the cost. Shop round - the price varies a lot. Eg. £1.59 each for a breeze block at Homebase, 74p for a better breeze block at B&Q Warehouse. Phone builders merchants for quotes.
Bulk concrete mixing is a pig by hand so think about hiring a mixer.
W.