Hi Dianne
We use a 4G connection in our rental house, while building, and it works very well, very fast and much better than the BT landline equivalent.
We have Vodafone unlimited 4g+ for £26 a month, but I think most mobile companies now offer an unlimited SIM. We regularly connect at 100mbits, but we are close to a town.
I agree, try the speed on your phone and see what you might be able to get. It would be worth spending a little more money for an LTE+ router, but only if your phone suggests you can get a fast connection where you live.