Brakes:
http://www.projectpuma.com/viewtopic.php?f=108&t=17129" onclick="window.open(this.href);return false;
Yes you can use your standard rear beam. For FRP width you need spacers:
http://www.ebay.co.uk/itm/Ford-Racing-Puma-20-5mm-9097939-Billet-Alloy-Rear-Beam-Spacers-Bolts-/170733692891?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item27c08567db" onclick="window.open(this.href);return false;
http://www.ebay.co.uk/itm/Ford-Fiesta-Ka-Puma-Focus-20-5mm-Spacer-Kit-Rear-Axle-Handling-Upgrade-/300737160099?pt=UK_Cars_Parts_Vehicles_Wheels_tyre_Trims_Trims_ET&hash=item460554e3a3" onclick="window.open(this.href);return false;
But shope for them... you get them much cheaper, or speak to williamsclio, he sometimes makes the 30mm ones