Thanks for the great responses. Preliminary study time is over and I've decided to buy this tracker. So we'll see..

Update.

The TK319-L GPS tracker arrived. I was pleasantly surprised how small it actually is. It came with a 5-wire loom and a tiny part-page user guide. There was an initial period of confusion as typical with new stuff.

I signed up with Spark for a 3 month trial starter kit. They sent 5 SIM. Cost nil. Eventually, using the Chinese tracker website Sky200, I got a result. Initially it put me 6km away, then it would go down for like 7hr. It might track live for half an hour then gradually each response would take longer. Then it might die altogether. Persisting, it seemed to improve with use. Then I took a drive with the tracker. I reviewed the route to and from. It followed it well.

Ok so I live in a marginal cellphone reception area. This might account for some of the initial reluctance to track however I thought this CAT M1 had a better reception and range? Next I want to test the device inside my tin shed. Normally any cellphone is all but dead in there..

Making progress..