So, after making just 4 value bets on one bookie, which shall remain nameless, I am now gubbed!! Gutted!!
They probably matched your browser ID. Google browser fingerprinting.
thank you!! i’ve researched this and will take steps to prevent it 
Which bookie?
Well I can say with 100% certainty that bet365/goalbet, unibet/kambi and betsson/clones are using fingerprints to identify and ban you and probably many other major bookmakers as well. My almost 10 years of multiaccounting experience tells me that it should be your no.1 focus point - even more than IP detection.