I am told that the lottery company can put winners in touch with financial advisors. A useful thing, I suspect.
I'd split the money up as well as as I could into multiple, relatively well-regarded banks in several countries. Well, as well-regarded as one can get today. I'd move some to Bitcoin, some to UK legal tender gold coins, not for investment but simply for (relatively) safe storage under my personal control. Try to balance my storage risk across countries and types of storage.
Then there's investment... that's another story. £100M is enough to decently balance fun/high risk/personal ambition/personal causes vs. low risk/long term growth/reasonable income.