I take it that you registered your domain name via Fastband?
As I understand it, that doesn't mean that Fastband "own" it and that you will have not have "lost" the domain name.
Whoever you registered it via would have registered it via Nominet if you had a .uk TLD who deal with .uk domains or ICANN if you had a .com TLD or other TLD's like this - but you should still be the registrant.
You should still be the one who the domain is registered to and there's a way you can confirm this.
Do a WHOIS search click here on your domain and it should report back that you ARE the registrant.
What you may need to do to get your site - and business - back online as I'm sure that's what you would like is to transfer your domain to another registrar.
Active Domain provide a service where you can make them your registrar click here.
It'll cost you to do this - and I would imagine it would cost at any other company that would do this for you - but at least you'll be able to administer your domain again.
Then you can arrange another hosting package and set up your domain to access your site via your new host and you'll be back up and online again.
Hope I've helped in some way.