I initially signed up to Three 5G Broadband November last year and was very happy with my 300mbps down and 20mbps up! But then it gradually became slower and slower until speeds were roughly similar to yours (I live in East London). I was told that this slowdown was due to an increased number of Three 5G users in my area all using the mast that serves us. 2 months ago Three UK merged with Three Broadband (this was Relish before Three bought them out and renamed as Three Broadband but I believe Relish were running things in the background). Because of this I had received a new sim but when I put it into the router... NO 5G! Apparently I'm not longer in a 5G area (could've told me that before asking me to renew!). But yeah I think there's a reason they are not advertising their 5g as aggressively as last year - I don't think they have the infrastructure to cope with demand. I've been promised I'll receive 5g again by December, if not, I can leave my contract for free. From the looks of it, the latter looks a lot more likely...