US tax issues including MLPs for returning Brit

[bess]

Hello,
A contact of mine has been living in the US for some decades and has taken US citizenship. He was originally British and has retained his British passport.
Now retired, he is considering returning to England but cannot see how he can manage his complex tax and investment/retirement affairs.
He is not cash rich but has frequent stock dealings and also has various retirement funds/savings plans including MLP, IRA and 401K.
Even as a US resident, he finds himself shackled for months around the time of tax submissions due to the complexity and the necessity of obtaining statements from each individual stock, etc before tax submission. These are often only issued days before the final submission date for tax.
I understand there are not just federal tax but also state, county and even city taxation requirements to meet.
He does not to wish to give up his US citizenship, at least in the short term.
Can anyone offer any useful advice on
1. how best to bring in income from such vehicles to the UK in a tax efficient way, whilst minimising conversion fees
2. how to find a financial advisor well versed in both US and UK tax laws. Those he has approached to date have clearly not understood less well known vehicles such as MLPs.
Thank you
Bess