I've just solved the problem!
I had to choose 'Other' when selecting my printer because Tronxy C5 was not one of the available templates. The default settings for MatterControl 2.19 had the 'Other' printer identified as an SLA printer. This didn't happen in earlier versions. So when 'Printer is SLA' was de-selected the extruder temperature controls appeared.
Hopefully this will improve my print quality issues.
Thanks for the help though!