Ha! I came to say exactly the same! I (my dad) had a PC1512, CGA with B/W screen. It came with a serial mouse that we only took out of the box when we used GDE. I have to say we didn't use it much, as we were used to DOS and the "I boot the computer and directly run the application/game I want to use".
My dad used Lotus 1-2-3 a lot (I guess that it was v2.2 or so in the Amstrad).
The original BBC computer was way to small for something like this, but you could get a version of the BBC Master that was able to run GEM:
https://en.wikipedia.org/wiki/BBC_Master
My dad used Lotus 1-2-3 a lot (I guess that it was v2.2 or so in the Amstrad).