That's interesting Simplyesl because I think there's the same explanation for both the points you raise.
Yes, Brits do say
Are you finished ? (as well as, not instead of
Have you finished?). By using it like this we turn it from a past participle into an adjective which describes a state rather than an action. (Compare it with :
Are you ready?) This often happens with other past participles (
tired, interested, excited etc) which are all used with BE to describe state. In other words, if we wanted to focus on the action we'd use it as a verb
Have you finished? but using it with the verb BE we're talking about the person's state of being finished with the task, and not what they actually did.
And I think the same thing is happening with
I was stood/sat ... Instead of describing it as an action, we adjectivalise the past participle and see it as a state. Interestingly this is exactly how other languages conceptualise it. French :
J'étais assis Italian :
ero seduto both mean literally
I was sat
PS: You know we can also say
I was just stood standing there ? But I don't think I want to get into that one ...
