A Downing Street spokesperson said:
The UK does not and will not recognise the Unilateral Declaration of Independence made by the Catalan regional parliament. It is based on a vote that was declared illegal by the Spanish courts. We continue to want to see the rule of law upheld, the Spanish Constitution respected, and Spanish unity preserved.
Link: Press release: Statement on UDI made by Catalan regional parliament: 27 October 2017
Source: Gov Press Releases