"ISTR that when 5G (or was it 4 or 6 or whatever?) being mooted it was said that because the range was so small the base stations could be like WiFi and instead of erecting the sort of masts they're now putting up they would be many unnoticeably small boxes similar to WiFi base stations on lamp-posts etc."
Yeah that was just PR hype. Microcells are small like this (and mmwave 5G does have coverage of a matter of city blocks.) But of course, just like 2G and 3G, 4G and 5G run on a variety of bands and for wider coverage the cell companies are going to continue to use the "cell towers" as well.
So there's (perhaps) 2 different technologies at play here (and I don't know if Vodafone is using both or not). 5G standalone is just as described, the cell cos started rolling out 5G for faster data before the spec was completely finished, so all "control channel" traffic ran over 4G, voice calls ran over 4G (if the company and phone support VoLTE, otherwise it could still run voice over 2G or 3G potentially). Running control channel over 5G is "5G Standalone", the battery life savings are mainly by not having to keep connected to both 4G and 5G. The 5G control channel does let it schedule time to send/receive data packets a bit faster so you get a slightly lower ping that way too, and save a slight additional bit of power since the radio can spend slightly more time powered down.
The OTHER technology is mmwave 5G. This is the stuff that gets easy multi-gbps speeds, Verizon got "in the lab" 5gbps over it 3 years ago and I've seen people posts for the last 2 or 3 years from places like Manhattan showing they could easily get 2.5gbps speeds in real-world use. The sites have a range of a matter of a few city blocks (because 28ghz+ frequencies get scattered and absorbed), but massive speeds. This isn't doing anything too fancy to get those speeds, they just run 400-800mhz wide channels versus the typical 4G/5G channels being 20-40mhz, so needless to say if you have a channel that's like 40x the size you can get much higher speeds over it.
The nice middle ground now, C-Band (5G bands n77, n78, n79 -- don't worry, I googled those bands I didn't have them off the top of my head.) This is 3.3ghz-5ghz range. It's used by satellite (not Sky Television, the giant dishes that went up first in the late 1970s and 1980s, and TV networks and such still use for uplinks), but in the US at least the FCC, cell cos, and satellite companies came to an agreement where the satellite companies are getting paid to move all their remaining C-Band stuff to one end of the band so the rest can be used to free up like 1500mhz or so for additional speed -- this is nice because it has FAR higher range than mmwave band, but (since it's a huge block of channels) should allow massive speeds. (For most cell cos, CBand alone will give them more spectrum than they have in all their other bands combined, so it should give a nice speed boost when they have it all up and running.)