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Is the only breach because of the fireworks? was that their fault in any event?
From you have written I would be minded to formally write to them and seek the return of your deposit in full. Invite them to pay this to you within 7 days failing which you will take the matter to the small claims court which you can do on www.moneyclaim.gov.uk From what you have written they do not have a claim on the deposit even with this 'breach' unless they can show you that it has a value (ie they have been fined for this sum). Otherwise from what you have written you are entitled to the full sum being returned. Happy to discuss and please rate 4 or 5 stars for my time.
My pleasure. can you please rate 4 or 5 stars.