OK I have sorted my issue on this issue that has been going on for a year and it was so simple.
ANSWER: A very good Internet connection (fibre optic)
My problem was that I wanted to access the Time capsule when I was on holiday or away from my network (orange home broadband UK with 3mbps download). I could access my iMac from my macbook fine on other Internet connections but the time capsule did not want to show in the finder. After endless phone calls to Apple senior advisors and data captures from them nothing really worked. Here are a few things I tried (cant be bothered to list everything):
I tried the Time Capsule on my mums Virgin media network (didn't work 3mbps download)
I tried bridge mode on my router and letting the Time capsule do the DHCP setting
I tried every other option in airport utilities 6.1 and nothing would ever work as I would either end up losing my internet connection or I would end up with double Nat issues.
I tried signing in and out of icloud and that did nothing even though the lights were green on the status.
After all of these things were tried I finally managed to get apple to send a replacement because after a year it was then only thing left to try but this still didn't work. I tried this Saturday the 22nd of September 2012.
My neighbor had BT fibre optic installed this week so I asked if I could try the time capsule on her internet connection and BINGO it work. I could access the time capsule from my macbook via my home internet and tethering 3G connection. In airport utility my setting are BASE STATION = Signed into icloud INTERNET = DHCP NETWORK = Bridge mode This was with bridge mode in the DISK = file sharing ticked (no access over wan option available).
Please let me know if anyone else sorts their issue out with a faster internet
Craig