I have the same kind of problems here in France.
While I always had 4G with my previous phone (Sony Xperia Z Ultra), I never (really never!) have any 4G signal now I have the Super.
FYI my carrier is Free (French carrier not using the 800 mhz band)
I'd like to have news on the 4g signal from other users in France.
The trouble I have with 4g is really wasting my experience with the phone. I consider it unusable for now.