British English has many ways to say yes without making a promise.
Leave it with me: I will look at it. It may or may not happen.
I’ll see what I can do: I will try, but I promise nothing.
I’ll bear it in mind: I will probably do nothing.
That could work: I am not convinced.
In principle, yes: Yes, but the details may turn it into a no.
We’ll see: Probably not.