Obviously advice on the Internet about finding free WiFi is not terribly useful... but...
For London free WiFi can be found at:
- Starbucks (when you buy a £5 Starbucks card, but you get the £5 back as caffeine - and unlike the US there is no daily limit, just a 2hr session limit).
- Refurbished (green) McDonalds.
- Coffee Republics.
- Wetherspoons (if you feel like e-mailing while drunk).
- Some small coffee shops, although not very many.
- St Pancras station.