I've had my say on this in January so don't want to say too much again. But for a highly risk averse person who doesn't mind their money eroding over time, Premium bonds aren't totally dreadful.
Just as a comparison though, over the last 24 months my stock market investments (which can go down as well as up) have returned 25% with my better performing funds running at over 50%.
Does this happen every year? No, but it doesn't need to.
Every investment is individual, an advisor really needs to understand someone's needs, goals and risk appetite before advising on how to invest any money. What I'm trying to get at is, don't take financial advice from strangers on the internet. If you've £20k+ to invest, speak to someone or research, a lot.