I don't want to mess with SIM cards et al - any recommends for the pocket wifi's available? Really just want it for GPS and internet. Staying in London but will be doing a few train trips outside of London.
the GPS is in the phone so you don't need wifi for that. If it is referring to maps you can download those to the phone when you have wifi.
Most trains these days have decent free wifi, but the older ones don't, and probably as you go north. There is free wifi all over London, and in a few places there are hotspots on the street.
What I'm saying is you can get a device but depending on what you are doing may not need it.