Cancellation property

[AnotherBreakfast]

So I'd been looking for a nice bucket and space holiday for our family (2 year old, 5 year old and the hubby) and thought I'd found a good property in a seaside town. Cottages.com required a £25 deposit, so I paid it to secure it for next August.
Fast forward an hour and a half later, I looked up the local beach which was apparently a dog beach (my eldest H A T E S dogs) and a google of this particular area brought up reports of murders and fights...
I very quickly contacted the company (within an 90 minutes) to cancel the booking. Naively I thought that all online retailers at the very least would allow 24 hours for a cancellation.
Cottages have come back saying I have to pay £250.
I've had a quick look online and it Citizens Advice and which? Both cite that companies can charge you but it has to be a reasonable and fair amount.
I think for a booking that lasted 90 mins and for holiday dates next August £25 is reasonable and fair - but would appreciate some professional advice

Their terms and conditions sate that, if you book a holiday with a lower deposit than normal, you agree to pay the difference between the deposit paid and the normal deposit (along with certain other fees) if you cancel. This is therefore the balance of your deposit, not a cancellation charge.

Most dog beaches are only dogs in part of beaches in high season. I'd double check you can't easily go to normal beach from the home and keep your booking if so.
Or pay the £250.

if you can and dont feel it would out you - maybe post the beach and people can tell you how many dogs its likely will be there?
ie my local beach doesnt tend to have many dogs on it?