This idea comes in several related parts.
Firstly, I understand the call price information when roaming is being revamped because the call price information shown for some parts of Europe is incorrect. That being so, the revamp seems to present a suitable opportunity to split the "international calls" and "roaming prices" information on to two separate pages. Perhaps retain http://giffgaff.com/index/international for the international prices and create a new page at http://giffgaff.com/index/roaming for the roaming prices. This will reduce the on-page clutter. Most people are interested in one topic or the other, rarely both at the same time.
Secondly, the Goodybags, Blackberry Goodybags and Gigabags pages each have a common navigation bar along the top of the page. I am now suggesting that a similar "UK Rates", "International Rates" and "Roaming Rates" navigation bar also be added across the top of the respective pages to link them together.
Thirdly, the heading "International SIM Card" seems to suggest that in order to make international calls, a separate or specific type of SIM card is required. This is not the case, but that isn't explained anywhere.