Mmmm - difficult to say without seeing it, but this doesn't sound right? I can't imagine why you would do this, unless it's to use it as a goods lift (which is not in accordance with the BS). I've seen shafts with a lift & stairs serving the floors above access level but stairs only serving the basement, but not vice versa.
I take it that there are no fire-fighting stairs serving the basement - just the lift? Could fire-fighters then reasonably expect to use the F/F lift to reach a fire in the basement and use their normal tactics of going to the floor below and using the stairs to get to the fire floor, but find themselves unable to due to the lack of F/F staircase?
Are the basement levels separated from the accommodation to the same standard as for a fire-fighting shaft? If not, the shaft could be compromised.
If it's a new(ish) building it might be worth looking in the Health & Safety File to see if there are any clues (but don't hold your breath)!