If I may take your questions out of order:
Has anyone tried?
Yes. Me.
I was wondering whether a remote control from one would control the other?
No.
As Roberts and Hama both use Frontier Silicon (I think the Venice module)
You think right. The Venice 6.5 module, to be precise.
I have a Roberts Stream 93i and the infrared remote control is fairly limited.
You got that right, too. I told them so last year at the Berlin Funkausstellung. Unfortunately, they've gone right ahead and used the same limited and not very haptic remote control for the updated version, the 94i. I'll tell them again at this year's show, but I don't suppose it will do much good. I might even take my Hama remote to shown them how it should be done.
The remote control used by Hama with, for example, the DIR3100 looks a lot better, as it has direct access to more presets and dedicated source buttons to instantly switch between DAB, Internet, FM, Aux.
Indeed. Which is a good argument for buying a Hama instead of a Roberts. On the other hand, the Hama radios do rather lack a certain stylistic appeal; in my opinion, anyway. Swings and roundabouts.
Hi. I'd like to know whether Frontier Silicon devices use the same infrared remote control codes?
No, they don't, which is why they are incompatible with each other. Now, in the old world of "legacy" Reciva radios, it was possible to edit the config files in one radio to make it respond to the better remote of another, and to decide which commands should be remotely controllable (and on the radio panel controls, too). But as far as I know, this is not possible with Frontier radios. On the one hand, they don't want people poking about in their software wreaking who knows what havoc (which is understandable), and on the other hand, brands don't want users "improving" radios instead of buying more expensive models.
Thanks
You're welcome!
PS You know about UNDOK, I suppose?