Hi robcfg,
the cursor keys work well for me in OP.
Use cursor keys & space key.
(Or use the mapped joystick as described in F1-info)
I know the FDC has problems to read OP properly. So sometimes it can fail!
So, no worries, when it freezes.
CPCInABox has very basic FDC emulation.
(Like JavaCPC, too

)
Problem makes the <copy> key in CPCInABox.
It's mapped to "ALT" key and this opens application's menu.
So you always have to press it twice.
(Or I need to map it to a different key, which is not easy because almost all keys are already mapped, because 4 keyboard localizations: EN, FR, ES and DE)