General availability of wi-fi in UK?

Generally I'd say wifi is available in Britain pretty much as in US. Last year we stayed in five B&Bs and two hotels over three weeks in northern England and Edinburgh. As I recall, both hotels and two of the B&Bs had free wifi in our rooms. Another B&B had a computer for guests in the hallway, which worked fine for us. Two of the B&Bs had no internet access. If you're booking accommodations in advance, you can check websites or ask about wifi. It's also available in coffee shops and highway rest areas. In London, and I'm sure other big places, there are storefronts offering internet for a small fee. I'd recommend bringing your tablet if you don't mind carrying it around. A smartphone might be easier but that's beyond my present technological and financial capacity!

I agree with Dick. Our experience is that we could find wifi at McDonalds and various coffee shops, among lots of other places. In other words, the sorts of places where you could expect to find it in the U.S.

Thank you both. That's pretty much what I figured. Just didn't want to lug a tablet around unless it was going to be plenty useful.

You can also find free wifi at the motorway rest plazas.

Depends ... If you're using a laptop and dongle it's great except mountains, Far north, etc. - SOME trainlines have it - free if first class. (for coverage maps go to any mobile phone site). Free wifi is not that easy unless it's in your hotel or you deliberately choose restaurants/places for their wifi.
S