OK, it was a bit more challenging than I suspected but I have the 0.85 board updated to 1.26.1 & connecting properly to the latest web interface.
I have to say, the documentation could be somewhat clearer in terms of which BIN to use on which board etc - I resorted to guessing in the end and fortunately got it right - even just renaming the file to have something like a '06-85' reference would have helped!
Many thanks for the advice above - much appreciated!