I never tried the Drobo with the enhanced guide switched off. It became clear very quickly that the Drobo simply could not handle anything to do with TV as a Plex server. It is great for storage, but really bad at processing any data.
The Drobo contains 5 NAS-optimised drives each of 4TB, with dual redunancy, with a 256GB SSD; in case anyone is interested.
The Drobo no longer has anything to do with recording or scheduling TV. It’s simply too slow.
The 2011 MacBook works fine, though downloading the guide takes a few minutes. I still have the enhanced guide enabled, though to be honest, I should probably switch it off, as it does not add any significant content. I’d wanted the same level of information on each programme as comes with the Freeview guide, but even the enhanced guide does not deliver that.
I’m still getting to know the set up and in fact getting used to a different way of watching TV. Instead of watching what is on, just because it is on, I can now record multiple channels in HD, and choose what to watch.
Previously I had only a Blu-Ray with two tuners, and a small HDD, so tended to record one thing while watching another and only record in SD to conserve HDD space.
Now I can record pretty much anything in HD, and only watch the things that I actually have a desire to watch (and incidentally, skip through adverts, if they are on).
I’m sorting out the preferences on the control panel, helping the rest of the family to use the system and so on.
At present the extended programme guide is quite a low priority. I’ll get to it once I have sorted out the best way of running the system, sharing the content around the family and accessing TV programmes.
All good fun 
And thanks once more for your help. I really do appreciate it.
D