The 'genuine' UK Psion layout is pretty much the same as the UK Gemini,with round brackets on Sh+9/0, angle brackets on Fn+5/6, square brackets on Fn+7/8, and curly brackets on Fn+9/0.
In fact, of the characters which are common to both, the only ones which have moved are the underline (from Fn+1 to FN+J), Euro (from Fn+E to Fn+4), and At (from Fn+4 to Fn+K).
As for the difference, while the same design agency was involved with both the Series 5 and Gemini, the manufacturers were in different countries. It's perhaps ironic that in the '90s, keyboards were very common and it was the silicon, screen, and other components which were cutting-edge; while now the silicon, screen, and all the associated bits are standard and off-the-shelf while the keyboard is where they're having to build up expertise...
