@winningballs Sadly I agree with other PPs who remind you that people can get very weird about money and where you might expect generosity to bring good vibes, it might not.
Also, I agree with people saying "it is not that much money" in the sense that this is probably not enough to be "set for life" unless you have, and keep, a very frugal lifestyle.
Here is one way to think about how much £1 million is: if you wanted to convert this into an inflation-indexed income for life, how much would that annual income be? Unless your life expectancy is less than about 30 years, and considering also the effects of inflation, the answer is probably about £20-30k per year. If you use more than that per year, then the winnings will run down over time, at least in inflation-adjusted terms, which means "not set for life".
So my suggestion would be: do not quit your job, do not tell people or the information will spread and people may start to behave differently, and do not spend nor lock up the bulk of the money. Take some time to think about what you want to do. If you work full-time, maybe you could go part-time and top that up with money out of the winnings in order to maintain or marginally improve your lifestyle?
If you own your own home and have repairs or improvements that are really needed, do that. If you have a mortgage, consider whether getting rid of that might be a good use of the funds. And if you do not own your home and would like to, then start looking but do not be in a hurry: prices may come down, perhaps a little, perhaps a lot.
In terms of how to "park" it to minimise loss of purchasing power to inflation, you can put a little bit into premium bonds, but you can put a lot more into gilts (UK government bonds); if you buy a duration between 1-3 years you will get a little over 3 percent if you hold to maturity, and the most you can lose if you want to get the money back before maturity is roughly the duration times the change in interest rate (so if rates go up 1 percent, a 2-year gilt would go down about 2 percent in value if you then sold it without waiting the 2 years. a 1-year gilt would go down 1 percent if you sold it without waiting 1 year). Or if that controllable risk of a small loss still bugs you too much, then you can put that full amount into an NS&I Direct Saver account which pays about 1.8% right now and is instant access and fully government-guaranteed.
Finally, if you want to be nice to friends, you could throw a big party or give them all somewhat more expensive Christmas gifts that are also thoughtful.
Hope this helps a bit.