It is far from ubiquitous. But many restaurants advertise it. And the quaint family-owned London hotel I first visited in 1980 has finally broken down and installed portable units in 10 of its rooms. We very nearly shouted hallelujah when we found one of them cranking noisily in ours. Canned Diet Cokes are kept in refrigerators, sold cheaply and taste right.
Ice is provided, sometimes even voluntarily.
Cold beer is ubiquitous, particularly Budweiser. It's served on tap, ice cold, everywhere. American travelers should be aware that lager beer's big attraction isn't so much the lighter, foamier taste and cold temperature. English pubs are still quaint and cozy. And the food's getting better.