Taxation for foreign investors?

[highterm]

How are foreign investors taxed for both dividends and gains when owning and selling-

-UK companies listed on a UK exchange
-Foreign companies listed on a UK exchange

Are taxes witheld by the country of the company (if a foreign company) or the UK?

And how would an offshore company be treated, if one was used as an investment holding vehicle?

Thank you

 

[Technically Fundamental]

Dividends - Income Tax
Gains/Losses - CGT

Offshore... I've heard about these trusts but its real knife edge stuff so speak to a specialist.