Where to put £75 pm?

[Matttrakker]

Evening, previously I've had friendly saving schemes over 10 years and got a reasonable bonus but it's not been a lot,
Now I'm out of these and looking to put about £75 a month away, I want to do it for about 10 years and not be able to access it easily.
What is the best way to do this, I honestly have no idea and appreciate any advice. I want a good return and am happy to look at it every year to change it. I'm not sure where to start really.
Thanks