Yes it's a concern and it's a big drop for one day, but it's not uncommon and 6-8 weeks ago the FTSE was substantially lower than it was at today's close, but that is just the nature of the stock market.
I think a lot of the Express (and other) articles are just more examples of dramatic reporting, today's fall actually only represents about 2.5% of the market value, despite being the large numbers involved:
Come the new year, it will probably climb back up again, as it does in most Januarys:
In fact you could argue that now is a great time to invest!