I'm on EE and I haven't seen 3G in literally months, I do not recall when I last saw it. I either get 4G or E, never 3G.
I do not suspect you will spend time stuck on 3G as you describe, simply as their 4G coverage is so good.
Network 3 prioritise 3G over band 20 4G, so I find in London I was on 3G a hell of a lot.
Edited by ukhardy07 (Mon 21-Oct-19 19:02:45)