Venue Slow to Issue Refund

chubbycheq

Nov 2019 booked accessible tickets for a concert in Jun 2020 at Southampton FC, direct with the venue. 
Concert cancelled due to pandemic. 
Rearranged date is May 2022.
I can't attend. 
Requested refund on 15/03/22.
Received automated reply that I would receive a reply within 14 days.
Today is 16 days. 
Called them.
They say they have 'requested permission from the promoter to issue a refund' and they're waiting to hear back from them.
Asked how long ago they contacted the promoter.
They said it would have been soon after receiving my email. 
That's over 2 weeks ago. 
Pointed out that they're legally obliged to give me a refund no matter what the promoter says,  as the date was changed. 
Got an email address for the boss so I can express my dissatisfaction but I'd really like to give a deadline and say that after such time I will be charging a fee.
Can I do that?
How should I word it?
They HAVE had my money for almost 2.5 years, after all!

Good advice will be gratefully received. 
TIA

Thrugelmir

Word it however you like. Unlikely to have any impact though. To effect a refund they need the money themselves. All takes time to process.