The first thing you need to determine is how long your investment timeframe is. Or in other words, when will you need to access your £50k. A good rule of thumb is that if you need to access your money within the next 5 years then you should just put your money into a savings account.
That is because investing in assets other than cash carries the risk of you losing money. Therefore the shorter your investment timeframe the greater the likelihood you could be forced to crystalise a loss. Investments move up and down over time so you need to be comfortable with this.