Complex DNS & GoDaddy question

[BioALIEN]

This was the only relevant place I can find on the forum to post this.

Setup Info:
- OS: Ubuntu 6.10 Server (used the Perfect Setup guide to get it all working).
- I got everything into one box (single IP, bind9, php5, postfix, mysql5, apache2, quota etc).

The Problem:
I have a domain (example.com) with GoDaddy, I have parked the domain with them using:
- park17.secureserver.net. [64.202.165.120 (NO GLUE)] [US]
- park18.secureserver.net. [68.178.211.113 (NO GLUE)] [US]

However, I want to rebrand the DNS for transparency and also to blend this into my own service for vhcs2 hosting etc. So I then created my own custom DNS using their Total DNS Control and created something like this (same IP):
- ns1.example.com. [1.2.3.4] [TTL=86400] [GB]
- ns2.example.com. [1.2.3.4] [TTL=86400] [GB]

Now I am required to manage my own DNS in order to keep example.com alive. However, it's common sense that GoDaddy's DNS is more reliable than mine so is there a way I can say something like the following in my BIND:
If my DNS (IP) is dead, default to the GoDaddy DNS to keep at least my email (GHA) alive?

I want to secure that mail should always work no matter whether the server goes down or not. For this, I've configured Google Hosted Applications to point to GoDaddy's parked domains rather than my DNS. But this didn't work so I had to also configure i on my custom name servers.