Thanks for the ideas, I will look into 3UK.
But I would have to have it sent to Canada, as that's where I live, -and-
LOL, why would you not be going to the UK? LOL

I really don't want any complications activating, I don't have a UK address etc... Is there additional cost to roam, as I will only be in London 2 days.
That's why the ease of simoptions appealed to me. I will be very busy upon arrival, and honestly find it stressful and confusing trying to figure out all the cell phone options in foreign countries.
But I have still yet to find anyone who has actually used them.
I am also considering KnowRoaming, not the sticker, but their new Global SIM card. It might actually suit my needs, and be cheaper than simoptions. Plus I trust they are a legit company. I am just a little concerned about download speeds. I have read conflicting reports. Has anyone used KnowRoaming in London England, The Netherlands, Belgium, and Luxembourg?
My main purpose is to have GPS, (google maps or similar) as I will be renting a car, but I would also like to be able to make phone calls, and send and receive texts back home to Canada.