Water damage to mattress - any advice?

Hi,
On New Year's Eve, the water tank in the communal loft, which holds water for the 5 flats in my block, leaked. Well, it flooded - my spare bedroom was like a walk-in shower room with the water pouring through the light fitting above the bed. Thankfully, my partner & I were home and managed within a few minutes to cover the bed with plastic, move it aside and put a plastic crate for the water to flow into.
The tank has been repaired and we are speaking to the insurers about a claim. Sadly, this is not the first time this has happened!
My question is regarding the mattress, which was already sodden by the time we managed to cover it with plastic sheeting.... We have been drying it out on its side in front of the radiator which is on morning and night each day. The outside feels completely dry and there is no visible staining on the cover. However, as it was so wet, I am concerned that the interior will still have some moisture in it and that it will become mildewed from inside, which I understand can happen.
Does anyone have any experience, knowledge or advice on whether I should just seek to have it replaced or whether it is probably going to be ok? It's annoying as it is fairly new and barely used, as it was bought after the last time we were flooded 3 years ago! :mad:
Thanks,
Claire