Refused to pay £52750.49 claiming game malfunction!

I played at net bet casino on a game spooky family slot and various other slots.When i received wins at a low stake i gambled them on double or quits red or black upto 5 times and played for a few hours.I then increased my stake and i kept winning.
I have supporting video but to large to upload and some screenshots of chat & email.I had no bonus restrictions or wagering requirements to full fill.
I withdrew £50,000 and left £2000 in my account.
Life changing amount i was so happy ;-)
The next day i played half a dozen different games and got my winnings upto £2750.49 as my luck continued.
I received an email the following morning asking for my documents and sent those in and received verification that those had been added to my file. I was then locked out of my account ;-(.
I have not acted in anyway shape or form outside there T&C and supplied all documentation as asked.
6 Days later i was called by Netbet on the mobile telephone after chasing up via chat all week with no firm answers other than were investigating.
They basically asked me if i thought it was strange winning on black? Its 50/50 is it not?i asked?
She explained that its not usual behaviour and i must of thought it was weird winning on black?
I explained that if you do your maths that its possible to flip a coin and it land on heads 3500 times on the trot so no I did not think this strange at all winning when choosing black.
I am not a game engineer and on the Netbet website its says the RNG runs in the background behind all games to ensure a fair game to all players,and that games are thoroughly tested by leading agencies, I thought it was how the machine would pay out as it didn't have a large JP or anything only a double or quits gamble.

They have offered me a goodwill gesture of £1000 but refuse to pay any of the £52.750.49p.
I have emailed them and said i think given the fact i won such a huge amount i would like them to send me the exact report of the bug in this game as required by law.
I anticipate and look forward to a fair, amicable and swift settlement agreeable to all partiesI am still waiting for a reply to my email and it has been 10 days since my win.