Unfortunately there are incidences of UK airlines putting pressure on crews to operate "outside" the the CAP's, MEL's and Ops manuals.
These are however very serious allegations and you must be totally sure of your facts and have plenty of evidence before doing anything about it.
You can be sure that reporting anything like this would get very ugly, very fast, but to be honest it is the right thing to do. However hard and risky.
With regard to FTL's, there is not really any excuse for not knowing them and implementing them correctly. That is our responsibility as crew, yes crewing and ops should understand them, but at the end of the day it is up to us to comply.
Most people are reasonable and will do all they can to "help out" in times of trouble, but I think this thread is more about being expected to push the boundries on a daily basis. For example according to my reading of CAP 371, if you know you will be going into discretion before you start the final sector on STD times, then discretion isn't really open for your use. Therefore to fit within CAP 371 you must NOT operate that sector.
I stress that this is my interpretation, but nobdy has been able to convince me differently, including our Ops dept.