I'm not sure if there ever was a Golden Age for Acorn. If there was, I guess it were the BBC days. That's not to say they didn't have times of great developments, I just mean in terms of market success.
You say Acorn wasn't big enough to sustain non-PC hardware and software development, but even Apple wasn't that big a company in those near-fatal days. And Apple has never abandoned separate hardware (and software) developments. In more recent times, they've adopted more traditional PC hardware, but I think when you'll open up various Macs you'll find a decidedly unconventional architecture, combining traditional PC hardware with untraditional design.
Like Acorn, Apple had spread itself too thin in even more varying endeavours than Acorn. Apple's renaissance began as soon as Steve Jobs returned to the company and cancelled a large amount of relatively fruitless product developments. The iPod was perhaps the most visible part of Apple's resurgence, but in fact it has been a combination of several factors. That's not to say the iPod didn't benefit Apple immensely, but concurrently Apple re-established themselves in certain key markets where they've traditionally had strong footing. Plus they reconfigured their main assets, laid off those not serving the company directly and placed bright minds in positions of power. While Apple bought NeXT to acquire their advanced OS, it were the NeXT people (led by Jobs) who subsequently took over Apple.
In many ways Acorn was Britain's mirror of Apple. Both extremely innovative companies in constant struggle against technological complacency and convention, due to their innovative mentality and drive for advancement. Nowadays Apple is sometimes referred to as the R&D branch of the industry and I can't say I disagree with that. If one takes the time and researches the company's endeavours, one will find a truly remarkable and recurring influence on the technological progress of the whole industry. From the first successful GUI to one of the first digital camera's, from QuickTime to the first PDA and to radical change when necessary (68000 to PowerPC to Intel x86, Mac OS 9 to Mac OS X changeover). Some might not realise this, but Apple technology (and indeed ideology) goes far beyond the company's own products.
It's not often mentioned, but ARM Ltd became a successful company because it was separated from Acorn on the suggestion of Apple, since both companies were already working with the design for a while. Acorn and Apple set out to develop the ARM further in 1990 and one should attribute the following successes to Apple as well - even if the original instruction set and design was Acorn's. To this day, Apple is a major shareholder of ARM Ltd and indeed the iPhone and iPod products contain Apple-branded ARM processors, now even running OS X. Some of you will remember Xemplar Ltd, the joint venture of Acorn and Apple? Well, while Acorn pulled out, Apple continued it and so inherited part of the educational market which could have remained Acorn's.
It's pretty pathetic when some people disregard Apple as some hip brand producing ordinary products in fashionable exteriors. Apple walks a very fine line of balancing careful innovation with successful marketing. In contrast to what some might think, design isn't about how something looks, but rather how something works. There's your clue to Apple's success.