The hdmi auto-switching issue is not really the Humax boxes fault, its the TVs.
The HDMI spec is borked, so it doesnt auto switch if you use different manufacturers kit. You can thank the HDMI working group for that little gem of thinking.
The Scart switching will switch to the Scart connection.
For HDMI you need to switch to HDMI connection.
They will be different inputs on your TV, you cannot tell the Scart to switch to the HDMI input.
The SCART connection is an alternative to HDMI, not a supplement. SCART is the old-fashioned analogue video interface commonly found on VCRs and the like, in fact anything for sending video to a TV before HDMI came along. TVs generally had an auto-switching mechanism so that when you turned on (say) your DVD player, it would automatically stop displaying the live broadcast feed from the tuner and start displaying whatever the DVD player was putting out. Even modern TVs (if fitted with a SCART socket) do that, and the SCART takes priority over live and HDMI.
Unfortunately, SCART is not able to handle the high quality video that the Humax is capable of outputting. If you want that, you need to connect the TV to the Humax by HDMI. HDMI inputs do not in general have any kind of auto-switching, so the only way to stop viewing live broadcast from the TV's internal tuner and start viewing whatever the Humax is putting out is to tell the TV to do it via a remote control button press. For that and several other reasons, I generally only view TV via the Humax so the TV is always in HDMI mode - but as the HDR-FOX is able to record two programmes and display a third simultaneously that is rarely a hardship.
Having said that, as we are only talking about the 9300 here which is (I believe) only StDef anyway, the SCART video won't be so bad - several people use it (or the phono connection) to send video to a TV too distant for HDMI.