If you're picking up band 7 (2600) then that's probably a "high capacity" area for EE, so they've added the band 7 capacity to the band 3.
Does that bear any relation to where they've implemented their "double speed" or "4G+" areas? The coverage maps always suggested that such areas were based on a smaller number of masts, so I always assumed it was extra frequencies + carrier aggregation that achieved those.
I'm not expecting any band 20 / 800 in my town, as we have a very good band 3 / 1800 service and really high speeds; and our town centre is bathed in band 7 / 2600 - giving 100+ mbps speeds on a CA device.
Ironically, I wonder if the opposite is true. The band 20/800 areas will propagate a long distance, but will presumably have to start from a mast with good backhaul ... so likely to be one of their "better" masts. The centre of an 800 coverage zone is likely to be bettered by 1800/2600 coverage ... as the 800 is really only needed in the outer zones.
On the other hand, a "better" 800 mast is likely to be one that gets long-distance coverage, which might be the opposite of a "good backhaul", town-based, mast.