I would collect my winnings and never tell a soul. It’s more fun to have money (and thus the potential for what you could do with it) than to spend it.
I’d probably give my mates a massive cash wedding present, anoymously of course. That would be funny seeing them try to work out who gave it, probably think they had some benevolent great uncle/aunt hidden away somewhere.
I’d a few nice dontations to struggling local charities.
Years and years later I might let it slip that I won a milli to my mates or family, just to see the look on their faces. That’d be funny too. Then I’d share out the cash I had remaining that hadn’t been blown on saville row tailoring and audiobooks