HL fund/ETF question – help deeply appreciated

Hi everyone, I would deeply appreciate any help with the following:

I started a LISA with hargreaves. I am planning to buy a house in 3 years and any extra funds would help a lot. Unfortunately I learned about LISAs only recently.

For the next 3 years I can add £4k to my lisa every year and get £1k bonus each year. Even keeping it as cash I ll get a £3k bonus and accumulate in total £15k to help with my first house buy.

I would prefer though to invest in a fund or ETF. I'm open to splitting between multiple ones too.

Which fund or ETF would you recommend considering the above amounts and time frame?

Thank you advance for your advice.