There might not even be any changes regarding the filtering between the Mk3 and Mk4, the Mk4 could just be to fit onto the new master socket.
I don't see the issue with installing master sockets yourself, as long as its a professional install. I have had two engineers out back when I had a line fault at the pole, and none of them commented on the master socket install, which by the way was moved to a completely different room from the original entry point. So as long as you know what you are doing you will be fine.Also I am excitedly awaiting for the NTE5C and new (mk4) Filter to become on sale somewhere, I really want to see if there is much improvement in line stats.
New NTE5 (Home telephone socket) Openreach are planning to start using the NTE5C and VDSL Mark 4 filter from June 2016 and have advised that there will be a national launch using 3000 engineers working on installation and repair activities. Openreach will continue to deploy the NTE5A and VDSL Mark 3 filter as it manages the run down and build-up of old and new stock versions. Openreach anticipate that NTE5C will be fully deployed by end of September 2016 when stocks of the existing NTE5A are exhausted.