Tui the travel company

I’m chasing a refund for a cancelled excursion due to adverse weather during a recent trip to Spain.
Their anti customer service defences have been at full throttle since their cancellation. It’s only 100 quid ‘ish but their lack of interest makes me even more determined to get customer satisfaction. I’ve completed a Barclaycard refund claim but am determined to get a satisfactory response from Tui directly. As a group we spend 38k every year with them so it’s disappointing that they can’t be arsed.
Their Director of Customer Experience is Sue Bradley. Can anyone offer advice on how best to get her or her PA or her department to respond.
An email address or a direct line phone number would be a start but their ivory tower seems watertight ??