I have reproduced you issue using the FME 2018 WFS reader. This does appear to be a problem with the FME WFS reader when reading data from this site. FME can only read one feature type at a time. I tested with another site (http://giswebservices.massgis.state.ma.us/geoserver/wfs?request=GetFeature&service;=wfs&version;=1.0.0 ) and FME seems OK with that, so it must be something to do with the WFS configuration that FME does not recognize. we'll see if we can get this fixed.
I've had that issue as well in the past, it seems that the 2.0.0 reader, which you'll want to use with the BGT service due to it's rather limited feature cap, can only do one feature type at a time. @MarkAtSafe could you please add my name to the list for this PR?
We recently fixed the bug associated with this problem:
Bug 83194 - WFS: WFS reader - can only read one feature type
The fix is available in the FME 2019 beta:
Build: 19014 (2019.0 branch) Comments: WFS reader: v2.0.0 - use enclosing parenthesis when multiple feature types are selected in the TYPENAMES KVP, PR83194, PR74464.
This fixes one instance of this error that is sometimes seen when querying multiple feature types:
|ERROR |<ows:ExceptionReport ...>
<ows:Exception exceptionCode="OperationProcessingFailed=" locator="GetFeature=">
<ows:ExceptionText>Join query must specify a filter</ows:ExceptionText>
Note that this only applies to WFS 2.0.0.
In 2017.1 I have that problem (of course) with multiple WFS services from the Nationaal Georegister
https://geodata.nationaalgeoregister.nl//DATASET]/wfs?request=getcapabilities
So the workaround is to use multiple feature readers... or upgrade to 2019