My mum won a million on a lottery ticket and stayed private. She was offered free financial advice.
The only people that found out were family, as she obviously wanted to buy a new house and give close family members gifts etc. E.g. she bought me my first car and paid for most of my £12,000 wedding.
If I won the lottery, especially a large amount over 10 mil, I would be staying VERY silent. I would let my mum and stepdad know about my win, but not really anybody else (yes even sisters etc).
I would buy a house almost certainly straight away, but nothing like a mansion etc, maybe a nice detached new build. People have been aware that I have been saving for a house and wanting to move anyhow. I wouldnt get a new car etc, but I would pay off my current one.
I would want a huge holiday but would likely say a work bonus helped pay for it. I would probably stay working full time as well for my own mental health and sanity. Remaining would be halved - half invested, half in the bank.
If anyone asked about my holidays (as I would be taking a couple a year etc), I would just tell them I got a payrise in work.
You'll find most people are quite reserved at asking about money and will take it at face value.
Those that go out buying mansions or huge estates, designer cars etc only have themselves to blame for being outed.