Can I be forced to upgrade or replace my front door if it is the door that was there when I purchase

If you own your front door under the terms of the lease and the freeholder considers that it is not properly compliant to current fire safety standards, you could be asked to replace. For example, if a fire risk assessment finds that your flat is fitted with an unsuitable door, the freeholder can ask you to replace it to bring the door up to the current standards

In some circumstances it might be possible to upgrade your existing door to meet modern fire resistance standards, for example by fitting a self closing mechanism. An upgrade will only be possible if the door is of solid construction, has the required thickness, and has the correct glazing. You should contact an accredited fire door specialist to check if your door can be upgraded to modern standards.