FHT 8W - any idea how to read?

Hi All,
I’ve just set up openhab 1.7.1 and am reading various FHT device settings - so far just the valve positions, and temperatures.
I also have an FHT 8W - the boiler interconnect - I believe it appears as an FS20 device as this is what i see in my logs:

11:59:49.520 [DEBUG] [o.o.i.t.c.i.AbstractCULHandler:239 ] - Received raw message from CUL: F039F283800FB
11:59:49.521 [DEBUG] [o.o.i.t.c.i.AbstractCULHandler:296 ] - Requesting credit report
11:59:49.521 [DEBUG] [.o.b.fs20.internal.FS20Binding:204 ] - Received FS20 message: F039F283800FB
11:59:49.521 [DEBUG] [.o.b.fs20.internal.FS20Binding:224 ] - Received command UNKOWN for device 039F28
11:59:49.544 [DEBUG] [o.o.i.t.c.i.AbstractCULHandler:239 ] - Received raw message from CUL: 21 900
11:59:49.544 [DEBUG] [o.o.i.t.c.i.AbstractCULHandler:278 ] - credit10ms = 900

In my item configuration file I have an entry:
Switch Boiler_Status “Heating on/off” (Temperature, Boiler){fs20=“039F28”}

which I thought might help me read the messages, and also possibly control what is essentially a switch. I actually don’t want to control the switch, but would like to be able to see if it’s on or not. (for those not aware, it reads the valve positions of all my FHT valves, and opens when demand is great than a certain set point %age - works great, so would prefer to leave doing this, and just read the status).

I haven’t worked with FS20 devices yet, just the FHT valves, so I might be doing something wrong. Just for completeness, I have
set in my openhab.conf, and no errors at startup (debug logs).

I’d appreciate any help, hints etc,