Once you have opened the account and deposited the cheque consider two more things.
As mentioned here, £85,000 is the max covered by any bank that goes under, so go into a building society and open an ISA savings account. Move £50,000 of it over to the ISA, next year after April, open another with a third establishment and move another £40,000 over. Leave £10,000 for easy access in the bank account. That spreads the funds and secures them. Unless of course you plan on doing anything else with the money.
The second thing to do is to write a will or update your will if you already have one. Spend a little but of the money, and it will only be a little bit, on a solicitor who can ensure your own bequests are met when the time comes.
Then enjoy it and treat yourself to something lovely.