ok so rough steps were (not sure which ones actually matter & this was all done from a Win8 x64 pc):
Download & install Nokia Care suite (see earlier in thread)
Download DC_template_development_v4.bin (see earlier in this thread) and place in the "C:\ProgramData\Nokia\Packages\Products\rm-821" directory (or wherever your care suite set itself up for)
Install "WinUSB Drivers<architecture>.msi" from "C:\Program Files (x86)\Nokia\Nokia Care Suite\Drivers" (assumes x64 PC)
Run Nokia Care suite then run Product Support Tools
Connect the phone and let it be detected
Boot the phone into testing mode
Open device manager & find all the unidentified devices (check by unplugging and re-conecting the phone) there were about 8 for me.
Right click on each one and update the driver manually, show all hardware and select "Nokia phone"
From Tools, Firmware Downloads search for "059R075" and download files
When downloaded open "RM821_059R075_1232.2110.1244.3_035.vpl" from the packages folder
Edit line 12 (<ProductCode>059R075</ProductCode>) with the code for the EE firmware (059R1W4) so the line reads: "<ProductCode>059R1W4</ProductCode>"
Turn the phone off and then on while holding the up arrow. You should get to the Nokia boot-loading screen (Nokia logo with a cog)
Then choose "programming, Recovery" from the product support tool
Choose the downloaded image & click Start.
If you get a warning about being unable to connect to the phone do what it says and unplug the phone & power it off (hold both volume buttons and power for 5 seconds) then plug it back in.
Keep your fingers crossed for 5 minutes...
Like I said, not figured out what bits were required or not yet. Might do some more playing about later on.