My daughter's London run-around bike is 15 years old. The brakes that came with it were in too poor a condition to adjust properly and the brake pads they use are not widely available.
Looked at the £12 - £15 replacement sets on eBay and decided to go for these instead. At £20 they are a little more expensive but well worth the money. Solid quality, all alloy, well made. No flexing that you would get with the plastic types.
The bike itself isn't worth much so I was never going to recommend anything more expensive - but it is ideal for getting to the station and back. With these fitted it now has good stopping power and decent adjustability with no ultra-cheap parts that are just going to strip.
Highly recommended for a low-end commuter bike or older MTB.