reading this thread makes me feel almost ready to pack up and go home.
Every system has its quirks, when you are used to them it makes life much simplier, given all the threads and experiences to date theres not one manufacturer today that hasn't had an issue or 2.
I am familiar with Texecom and getting to grips with the Risco stuff, and touched on other equipment.
Back to the original question of the thread, the FM works fine if its setup correctly, first thing is to make sure the system is setup as 0UK rather then the default value of 0EN, I had a similar issue when I was first looking at the kit.
The signal strength, you should calibrate and adjust for noise, I have texecom hard wired and wireless around the office and using the Agility 3 wireless no issues, not to mention wireless heating controls and not a problem at all with intereference on any thing.
If you are struggling their tech support people should be able to help.