The Towering Inferno has been available on dvd for years.
The original R1 release had 5.1 sound but was not anamorphic,while the UK release was,but only had standard surround.
The new release(last week) is on R1 only.
While The Poseidon Adventure will be out on R2,UK release rights for Towering Inferno are held by Warner,and its Fox who are releasing the 2 disc sets in the US,so you may have to get R1 for TTI.
The Swarm was a bit of an Irwin Allen disaster in more ways than one.
However,the DVD release is of the extended tv version and contains about 40 minutes of extra footage not seen on Sky Cinema or on tv before.
Of course,most will say its long enough already