That also occurred at a hotel here in Cornwall. It resulted in the hotel owners going out of business.
What constitutes illegal discrimination is currently very specific in the UK. Discrimination is illegal under the
Equality Act 2010 when it involves treating someone unfairly due to protected characteristics—age, disability, gender reassignment, marriage/civil partnership, pregnancy/maternity, race, religion/belief, sex, or sexual orientation.
Refusing a booking on political grounds wouldn’t be illegal, whilst because those involved are gay would be.