UK tax treatment of US mutual funds in an IRA

Can anyone tell me how a UK, and naturalized US, dual citizen, resident in the UK, would be taxed on mutual funds held in a US IRA and 401k. When I move to the UK I'll stop contributing to my US retirement accounts and just reinvest the dividends.  Lizzit once told me that it's quite complex, but that they fall under the tax treaty. If withdrawals are made after age 59.5 does the UK simply tax them as income or am I going to run into issues with "distributing fund status" as well?

I've been thinking about my question in light of the remittance rules and the the UK CGT exemption and reporting fund status. As my mutual funds are in a 401k I believe there's no tax liability in the UK or the US for me as a UK and US naturalized citizen resident in the UK
until I start taking income from them. As I'll be remitting the money to the UK and it's income  it will be taxed as such by the UK, who I think gets first call on the tax as I'm resident in the UK and it comes from a pension. So I should end up with little or no US tax liability.

Is this correct?

I don't know the answer. I'm just replying to the thread to "bookmark" it. Though if anything's left of my 401(k) when I turn 59 and a half, I'll be lucky.