First-time investors, quite frankly, do not have enough experience to accurately assess their risk appetite. You're willing to "gamble" with that £50/month, but that's because it's just £50, and you're understandably salivating over that "42%".

That wears off. Over time, you'll be investing £thousands. (In ten years, you'll have put £6k of your own money in.) And the more you've accumulated, the more your "naturally quite risk-averse" inner self will start to take over, because it's no longer just a lottery ticket — it's an *investment*, that you've put a lot of money into and don't want to lose. But that +42% can fluctuate wildly; it can be -20% one year, or even -80%. (In your case, your losses are fortunately limited to 100%.)

Will you be mentally OK if your £thousands shrink even faster than you can invest?  
Can you keep your inner self from second-guessing your decisions (or worse, cashing out what you have left) while you're losing money?  
Will you still have the discipline to put your monthly £50 in?

*That* is risk appetite...and *that* is what "high-risk" investments require of you. The thing is, like courage, people don't know you have it (least of all, you) until you're actually in situations that require it.