UK taxation of US municipal and corporate bond

Hi,

I would like to buy some US corporate/municipal investment grade bonds via a US broker.
I just want to know how much those bonds will be taxed in UK and if it will be with CGT or or with income tax.

If it goes with the income tax will be this cumulated with the income of my job or is a separate calculation?

Is there any other way to make tax effective this investment e.g. ISA accounts?

Thank you very much