Bonus winnings "confiscated" unfairly

I successfully "opted in" to a Betsafe bonus offer on 12th January 2017. The offer was deposit and wager £50 for a £15 bonus with 35x roll over requirement. I wagered the full £50 (losing) and 2 days later accepted the £15 bonus. I span £1 spins, completing the wagering requirements with a final account balance of £974.25. Having made a full withdraw request on 14th Jan, I received an email 2 days later saying my winnings had been confiscated. The following reason was given

12.1 Any Bonus is only available once per person, family, household, address, e-mail address, credit card number, bank account, telephone number, computer/device and / or IP address.

20.1 If we suspect that you have breached these Rules, we may refuse to open, suspend or close Your Account. We may also withhold any money in Your Account (including the deposit) and set off any money or damages due to us against the money in Your Account.

I can confirm I am the only person who has lived at this address for the past 10 years with a Betsafe account. I do not hold an account with Betsafe under any other name, with my or any other bank account, email address or phone number. I am unable to prove this but I can categorically say that Betsafe cannot hold any information to the contrary as this would be impossible.

I sent the following to Betsafe:
Dear Madara,

Further to my email yesterday which I understand is now with the relevant team, I would ask that the following information also be forwarded on my behalf.

Firstly I would like to confirm that I (removed), email (removed) am the only individual residing at (removed) with a Betsafe account. The only other person living at this address is my mother (removed) who has personally assured me that she does not have or has ever had a Betsafe account, or any other bookmaker account for that matter.

I would like to point out that since I opened my Betsafe account, I have used the site on a few occasions, two of which resulted in a withdraw request. Both the withdraw on 24/07/2016 and the more recent withdraw on 12/12/2016 were successful, with no issues being raised. It is with this in mind that I indicate my good faith when completing the promotion on your site last week. The promotion was showing on site when I logged into my account, I was able to opt in to the promotion successfully, deposit and wager (unfortunately losing) and the £15 bonus was applied to my account 24 hours later. No issues appear to have been flagged until I was successful in completing the required wagering and attempted to withdraw my winnings.

Finally should a favorable response not be forthcoming with regard to allowing my withdraw, may I ask you to confirm that with regard to your internal dispute procedures all avenues have now been exhausted. In addition I request that all information pertaining to my account be forwarded to myself in accordance with current Data Protection protocol.

On a more personal note due to financial constraints I am not often able to indulge in online gaming. The excitement and elation that I felt on Saturday when completing wagering with a £974.00 balance was I believe akin to winning the lottery! I cannot express my feelings when I received your email on Monday "confiscating" my winnings. This has not been a pleasant experience and I sincerely hope that this matter can be concluded satisfactorily without the need for further action being taken.

They are still stating the reason for not paying is a breach of their terms 12.1, which is not the case.

I am hoping you may be able to intervene on my behalf, and avoid the more lengthy legal route.

Many thanks.