UK-wide WiFi is a nice idea, but the devil's in the details

The Cloud is planning to roll out blanket WiFi coverage in UK cities. It's an interesting idea in the short term at least, but:

1. How is billing going to work for roaming users? Will there be a single payment point or will you have to set up new payment details for whichever ISP you happen to be connected to at that point?
2. How much will it cost? WiFi access still isn't as cheap as it could be?
3. What will happen to existing WiFi networks? Many are already causing interference with each other, so the addition of an ubiquitous network is undoubtedly going to cause problems for incumbents.
4. What will happen in the mid-term, when WiMAX comes online? Will all these nodes be converted to WiMAX or can we expect an eternal WiFi network to fill up our radio spectrum in perpetuity?
5. Are there the resources to cope with this? That's an awful lot of nodes draining an awful lot of power and using up an awful lot of bandwidth
6. How will each node get Internet access? Wireless extension, wireless mesh or some other system? Or will every node have to be connected to a phone line? And will there will be enough IPv4 addresses available to cope?

Let's hope these issues aren't ignored or skirted over, otherwise there's going to be a great deal of effort being wasted.