mobile phone on trip to Scotland

Grobian

I'm going to Edinburgh for 5 days next week. I want to use my phone there, specifically I need mobile data. (for communication back home and also catching pokemon, otherwise I would probably just use the WiFi in the hotel / conference centre) I can live without texting/ phone calls, I never use those at home anyway.

Can I just walk into a shop and get a prepaid sim card that works out of the box? Will a shop be open on Saturday evening? Should I just do this directly at the airport?

What providers should I look at? (maybe someone can chime in with coverage or whatever)

edit:
I just saw that my home provider offers 100 MB for 3€ (resets after 24hours) or 200 MB for 10€ (resets after a week), so I guess I could just buy 5 day passes for 15€. That's hard to beat by a local provider, since I do need the actual simcard. And 100MB/day seems fine, I'm probably on WiFi for most of the day anyway. I would need something like £10 for 1GB to come out better and make it worth it to actually exchanging the sim card etc.

Librarian

The last couple of times I crossed the border from Germany to Denmark my provider actually sent me an automatic text detailing my options and I could upgrade just by texting back.
It should be fairly easy to set up and is definitely cheaper than trying to find a local solution.

Grobian

Yeah, I did it before for shorter stays, I just figured for 5 days there might be something better local. Also I expect to use a bit more data than usual for the pokemon thing.