SIMs - your best bet is a GiffGaff SIM. SIM is free, credit doesn't expire provided you use the SIM to make a chargable call at least every 3 months. Most UK SIMs will only keep the credit for 3 months.
I have the first one linked in a caravan. It works. Its not amazing. It may depend on signal strength but I can only get about 3 or 4 days out it if not charging off the van battery. It will detect shocks, speed, movement. You can interrogate it for position by sending it a SMS with the word WHERE. You can also switch to a data mode and use an Ap - but it would be data hungry IMHO.
Not 100% convinced the external antenna one would make it anymore usable in a container. I think you want to know its been nicked before it gets into the tin box!
TK102B - I looked at - but needs USB power so meant spending £3 on a USB power source which felt pointless the other one uses 12V power which I had plenty of. Plus its marked all over the outside what it is. The other one can be got for about £12 if you hunt hard enough and looks more like a car part.
Mine if it thinks its been nicked phones you. There may be a microphone on it - not sure - complete pain in the ar5e! Fine if it really is nicked - I forgot to switch it off when towing the van one day - I was called constantly by it! Cancel the call it goes to voice mail...
If anyone wants a GiffGaff SIM I wont complain to anyone using this link: https://www.giffgaff.com/orders/affiliate/shinyshoe
- which gets me free credit when you top up the first time ;-) - costs you nothing more.