We visited a block of flats in Southsea yesterday, as the owner had correctly identified that work needed doing, from both a security and safety point of view.
Individual flat doors need a lock certified to BS8621. I have mentioned before about BS3621 being the standard for front doors to houses. BS8621 requires the lock to pass the same attack tests, but allows the use of a thumbturn to open the door from the inside.
If you live in a flat, but your entrance door lock does not conform to this standard, please upgrade it. You will probably find that your home insurance company requires it, and the cost of upgrading will be much much less than the excess your insurers will deduct if you make a claim.