I once had about £20k in Premium Bonds. That was all my savings. I won a few times but only £25 a time. Overall effective interest rate was pretty poor. Its not great. I keep £100 in now, just in case. Thats now £125 thanks to another win. I've also had £5 worth since I was born (late seventies - its never won anything).
The rest is now in Index Trackers and similar. I've done the same for my son.