Here's my update:
Called customer services on their freephone number and got through straight away.
I explained my 2 main problems (TV not responding well and freeview box not responding at all).
The pleasant chap tried 9 separate downloads to my harmony (one by one...I was on the phone for 1h 20m in total) to try and find a code that would work my TV. Eventually we got it working ( albeit with some extraneous buttons, but that I have sorted easily).
The bigger problem was the Nokia Mediamaster which he just couldn't get to work at all. After talking with a superviser, he sent me an email with a beta version of a new firmware update. Apparently some devices (including my Nokia) require a higher bit rate to operate than the harmony could provide.
The downloading of the firmware was simple and now the Nokia works fine.
It's just as well that I was able to speak to the helpline while connected to the net, or I don't think I would be sorted still.
So, now all my devices are recognised. Some features will have to be learned raw, but that's easy enough.
What I am still not sure about though is the "Watch TV" , etc. buttons.
In our house, maybe the tuner amp will be on and switched through to the kitchen speakers while someone else is watching TV in the lounge (as an example). The harmony creates havoc with this kind of set up. I suppose it's not the harmony's fault - but I'm wondering if I can work around it. At the moment, I'm not using this feature and am just using the device button to control individual items as required which works OK but is not as simple as hard device buttons like the ones on my old OFA 5.
It's great to be able to rename and delete and move buttons around using the web wizard and the transmitter is strong too. Unlike my old OFA (which could never control the up/down button for the Nokia, nor the TV's text buttons), it has learned every command I have tried on it. Even the complex sub menus of my Tosh HDD/DVD recorder can be easily accessed. It sits well in my hand and I am very quickly beginning to warm to it's features.
The Activity buttons are, at the moment, my only gripe. The ones I have set up are unreliable (this may very well be my fault though).
So, after an agonising and infuriating first day out of the box, things are much better now.