For what purpose? I ask given that you have so many speakers. How and where would you used them?
Audio Visual On-line has the Diamond 155 for £250/pr while supplies last. That's half price on that speaker.
The Diamond 122 has a 6.5" (165mm) bass driver, and though it may not seem so, that is TWICE as big as the Diamond 10.1's 5" bass driver. Also the Diamond 122 will go down to about 40hz. Though the Diamond 10.1 are good speakers for the money.
The difference between the Diamond 122 and the Diamond 10.5 is that the Diamond 10.5 has the addition of a Midrange driver and a larger cabinet. The Diamond 10.5, because of the larger cabinet, has about an extra 5hz on the low end over the Diamond 122, though both are well below the frequency you would need to run a Subwoofer. That is, if we assume an 80hz Sub crossover, both speakers are well below that. And on their own both are more than capable of standing as good Stereo speakers.
The Diamond 155 have better drivers, but a less elegant cabinet. That was a compromise that Wharfedale made. To give you drivers based on the new Wharfedale Jade Series, they had to cut back on the complexity of the previously curved sided cabinets. So, to hit the price point, you gain in one area and lose a bit in another.
I've not seen reviews on the Diamond 155, but both the Diamond 121 and Diamond 122 got very impressive reviews. Indicating you could expect similar results from the Diamond 155.
And once again, the previously £500/pr Diamond 155 are on close-out for the very modest price of £250/pr. That's a pretty outstanding deal. Unless you specifically need Bookshelf speakers, I say get the floorstanding. But ... limited to available stock.
So ...when, where, and how you are going to use the speakers is probably the determining factor.
Steve/bluewizard