Any suggestions as to what Sim Card provider I should use in London and Belgium. I will use it to get directions from either Citimapper or Google Maps in London, and Google Maps in Belgium. I don't need to have phone service. I'm a bit hesitant to rely solely on WiFi.
Assuming you have an unlocked phone, stop in at an EE store in London upon arrival and they will set you up. We did so last year for a 5 county trip. Worked perfectly.
I bought a Vodafone SIM and plan last year. Worked fine in both London and Switzerland. I’m planning to do the same this year.
Carphone Warehouse will probably have a wider choice of providers.