Looking for Advice on how to save and invest money

I have recently gotten a lump sum payment from my partner's passing, about £370k

I am seeking advice on how to best save and invest the money. I am looking to have some of it "locked away" and some more easily accessible (not necessarily instant access but something that would required paying penalties to access funds).

In addition to prior knowledge, I have been reading more about different things including: Vanguard's Target Retirement Fund and LifeStrategy range. Also about cash ISA's, Gilts, NS&I's

Unfortunately my spouse passed within a few months of buying a property and now I will try to take over the mortgage. I don't want to sink money or a lot of money into the mortgage (this money was paid in trust so didn't pass through the estate). Just for the sake of my and our kids' stability, I wanted to take over the current mortgage until I have decided whether I wanted to sell this property or rent it out and buy somewhere else. So this means that, potentially in the next couple of years, I would need access to about 200-250K to put down as a deposit on a similar property but in a more expensive area (closer to where my spouse is buried and just an area we always wanted to go back to)

Essentially my question is, how can I best diversify this money where I can lock at least a 160k away in one of vanguard's schemes/ranges and invest some of the rest in gilts, cash ISAs, etc. while paying very little to no taxes on any interest earned or capital gains legally of course.

Also is this something I can do on my own just by reading and learning or would I inevitably need a financial advisor?

P.S. apologies if I misspoke at any point and happy to clarify any points. Many thanks in advance to anyone who would like to offer advice!