Question - if a US citizen wants to transfer USD to a UK based USD account - is there any tax implication, either to spouse or to same persons account?
Thanks
No. It's already your money and you've already been taxed on it (if it was subject to tax). Taxes are applied to income, not to your existing funds*.
* Interest on savings, as well as capital gains,
are subject to taxation.
Out of curiosity, why do you want a UK-based USD account? With online banking for remote access, why not leave your USD in the US-based account and manage it from here? If you're transferring it over, I'd recommend converting it to GBP. Transferwise will move it and convert it for extremely low cost.