I assume this confusion arises because you live in the Midlands and so English isn't your first language the answer is "it's closed" .
Very good! Based on many years of flying in UK and Europe I would say the answer is whatever the operator decides. Many will in fact be open with no services, unlike your local supermarket where closed is not available at all. My local airfield used to put up a notice at this time of year saying;
"Airfield closed 25th Dec and 1st Jan with no services. Please obey noises abatement if you decide to fly and remember we are not licensed".
Closed - in the UK - is whatever the operator wants it to be.