I'm about to come into some big(ish) money, and I can't stop spending it (even though I won't have it for months)

Here in the UK you can invest up to £20,000 per year. Over the years, your liability for tax diminishes (I’ve had mine for over 7 years, so now pay no tax.)
The interest rate varies according to economic circumstances…

There are all kinds of complexities between qualified and non-qualified IRA beneficiaries. And it has changed several time in the last couple of years. If anyone is googling for answers, make sure you know the date each cite you’re reading was written.