If I withdraw money using my Curve card from cards linked in the account will my limit of 800£ be reduced from the Curve limit or from the Revolut or any other card linked to the account?
When using with revolut - limit will be reduced from Curve limit. Revolut sees it as purchase.
With other cards - it depends on policy of those linked cards. Some banks might treat it as cash withdrawal.
Cash withdrawn are reduced from your withdrawal limit. Be careful on what card is your underlying as they may charge you.