If the ULA died, the computer was e-waste. This was the antithesis of the Apple II (which had socketed TTL chips). This trade-off (unrepairable vs. affordable) defined the British home computer boom.
Chris Smith’s The ZX Spectrum ULA: How to Design a Microcomputer If the ULA died, the computer was e-waste
Early prototypes suffered from visual "snow" on the screen because the ULA and the processor were fighting over the memory at the same time. Altwasser solved this by "contention"—making the processor wait its turn while the ULA drew the screen. The Crisis: The Ferranti Deadline If the ULA died