I went to the Waitrose car park again today. And I did lots of tests. I tested 1p mobile, Lebera, Voxi, Tesco Mobile and Smarty.
Straight off the bat Tesco Mobile failed as it showed full bars but refused to run a speed test in speedtest.net.
1P Mobile wasn't overlay impressive, compared to the others. And Lebera Mobile was NOT as fast as Voxi.
Out of the sims I tested first place was Voxi followed by Smarty, it seemed Voxi had better download speeds whilst Smarty had better pings and upload speeds.
I'll test further between Smarty and Voxi. But for my area it does seem Voxi is the faster signal. And then it's a conundrum, stay with Smarty or move to Voxi, but 3 will be switching off the 4G and may end up outperforming Voxi. I'm in North Dorset so don't hold my hopes for 5G getting to me soon, and then it's a case of who is more likely to provide it, Voxi or Smarty. But that's in the future.
Here are my screenshots of the best speeds from my tests for 1p Mobile, Voxi and Smarty, I haven't posted the Lebera ones as I can't remember which one's they were but they gave a speed of around 60 to 70mbps.