OK seemed to upgrade OK but Error generating preview :

*EDIT* Preview now works, second time round!

Running "less:compile" (less) task
Fatal error: {
"type": "Name",
"filename": "src\\core\\less\\base.less",
"index": 493,
"line": 25,
"callLine": null,
"column": 17,
"extract": [
" .focused, button:focus, select:focus, textarea:focus, a:focus, input:focu
s + label {",
" outline: @focus-outline; ",
" }"
],
"message": "variable @focus-outline is undefined"
}