I guess it depends on how much time you want to put in.
Ultimately, if you do a ton of research and keep up to speed with everything, the likes of FreeTrade and other platforms will give you the most customisation.
If you want to feel like you are doing something other than leaving your money in a current account or low interest savings account, the “robo advisors” are your next best bet (as you’ve found out with Nutmeg).
You’ll find a fair bit of disdain towards them from people who are familiar with other options that provide a more bespoke service and are comfortable investing their money and taking 100% of the responsibility.
But from my experience (and from speaking to others), it can be a happy medium.
It can also be frustrating when the market drops, and you find that you’ve lost money despite not actually doing anything yourself - But that’s just part of the rollercoaster that is investments!
If you’ve got the time to research - A FreeTrade type service will be great.
But if you don’t, I wouldn’t dismiss the robo advisors