All - me again from the post above.
LOADS of updates of all types including Windows, Security, Office, Microsoft .NET etc. It has taken about 11 hours in total to download and install all the updates after refreshing using the USB stick. I specifically excluded KB3033055 which was one of the updates offered but I did get a firmware update in one of the early (last evening) update packages that I don't remember from the last few days of resetting and installing updates. It may have been there but I didn't notice it previously.
RT now running 'normally' so MAYBE it is 3033055 which causes the problem - but I am reluctant to let it just install in case it brings the machine down again. It may be installed automatically at some point which could screw me up once more or MAYBE the firmware update handles the problem.
I have now created another recovery drive at the current standard of install - if anyone knows that this is going to be different to my old (pre loads of updates) recovery I would like to know please.
Another point - mine is a 64Gb model. When I first reset it on Sunday last the software consumed about 11Gb in total. After updates and then Cleaning System Files with the built in Disk Clean Up utility this dropped to about 8Gb but now (after a refresh from the USB and 11 hours of updates it is almost 20Gb - this is why I searched for a 64Gb model and not the 32 (which a friend owns and which ran out of storage because of uninstalled updates - which was her own fault but that's a different story). I am now running Disk Clean Up again and it is going to remove the Windows.old folder which is about 1.5Gb but not much else.
Onwards and Upwards!!