After my initial post I gave up on the idea of using the tablets internal GPS and have had great success with using Avenza with a Trimble R1 Bluetooth receiver. It works perfectly fine after pairing with the Trimble app and shows up in the device list.
In your reply to i.scott you mentioned compatibility with Garmin receivers. Do you know if the Garmin GPS 18x USB receiver (https://buy.garmin.com/en-AU/AU/p/27594) is supported? The only reason I ask is because the USB model can only output data in Garmin proprietary format where as the DB-9 pin serial connector version outputs data in NMEA 0183 format (industry standard) or proprietary Garmin format.