Clarify the context here just in case I am missing your point. See my answer to Hussman. Web traffic on 3 has timeouts and horrendous delay on some pages loading. If this happens I try it on my Samsung which is on the EE network and the pages load straight away. Same location, same timeframe.
You stated the OP had an issue with Three. However, the OP has said that he was able to use his phone to connect to the Internet using 4G on the Three network despite not being able to via his router which was also on Three. This indicates it’s a router related problem.