Further help required configuring secure wireless "public" hotspot

I believe what Anglo mentioned above would work if the sonicwall can do the necessary NAT and dhcp on the DMZ, although it would require multiple public ip addresses.  It would also require that the wired backbone for the wireless network be physically separate from your existing network infrastructure.

How many access points are planning to use?

Probably the simplest way to do it if you need multiple access points would be with a centrally managed wireless setup.  Something like the cisco smb access points and controller or a controller and access points from Ruckus Wireless (I haven't used Ruckus wireless stuff but I've heard good things about them).  Finding a solution with PoE support shouldn't be a problem, but these setups aren't cheap.  With pretty much any centrally managed wireless system, you should then be able to configure firewall rules that only allow wireless access to external ip addresses, and block all internal access.  For a public hotspot, it would also be a good idea to block traffic between wireless clients, as any such connection is most likely malicious.  This is typically an option in the configuration as well.  With a centrally managed setup, you can also do more advanced things such as multiple ssids.  This would allow you to set up 2 wireless networks on the same hardware, making the one open for public wifi and securing the other but allowing internal network access for your own/your companies internal use only.

If this is just a small setup and you are only planning to use one access point for public access, then the simplest solution is a single router with decent firewall/configuration settings.  I have done something like this with a buffalo whr-hp-g54.

Thank you both for your comments!

The installation is intended for a new Pub. One WAP in the main bar area and a second WAP in the conference room. Due to the fact this is a new business, unfortunately budget constraints would not stretch to installing a wireless controller unit.

The PoE can be achieved by using a couple of single PoE injectors which can be purchased for approx £30 each. I have been asked to use the existing 2-Wires router that is currently the internet gateway, and try somehow to use some budget Wireless Routers/Access Points to create 2 additional wireless networks, which I had intended to have on 2 separate subnets from the internet gateway.

Would it not be possible using static routes and/or RIP to route internet bound traffic from the 2 "public" subnets to the internet gateway on the private subnet, whilst blocking public access to the private LAN as suggested by i2q2 in the related question? If this is possible what settings would need to be configured on each of the routers/access points?

I'm starting to think that the simplest and best solution would be to have a second internet connection for public access.