I know this forum isn't the best place to get specialist financial advice, but here are my thoughts, for what it's worth.
A lump sum pension payment isn't just a lucky windfall, it's supposed to give you security in your old age. Assuming it's a substantial amount, I think you should take proper financial advice.
Premium Bonds are getting a lot of mentions here, but it's not a sensible way to invest large sums. What you're doing is keeping your capital safe and gambling with the interest, and without a big win, the actual value of your capital will dwindle. That's fine for a bit of a flutter, but it's not a wise way to invest all your savings to provide for your future. The overall rate paid out is now about 1.4%, and because a few people get big prizes and this is just an average, most people won't get as much as this.
By tying up some of your capital for longer, you can get a better interest rate than this, and one you can rely on, so your savings don't lose so much in value. Do take some advice on this.