Voip over Orange 3G

I am trying to get my Nokia E61 to make Voip calls over 3G. I am running the latest 3.xxxxx firmware with the new SIP settings application. I had some limited success with T-mobile but the signal was awful so the call was broken up. Orange has a much better signal but I have a feeling they are blocking all UDP traffic as I am getting no registration at all? Anybody know if this is true?
I connected the the phone to my laptop as a modem and ran your port tester which said failed for everything but that could be a laptop phone issue I guess?
Is it possible to configure my Asterisk server to use only TCP traffic?

Where would you like to start with the bad news?

Yes Orange do block SIP.
Asterisk does not do SIP over TCP, besides which:
TCP connections cause their own problems for VoIP.
Nokia E series phones are pretty bad (VoIP wise).
3G is pretty ghastly in terms of maintaining a suitably steady connection.

Otherwise no problems

OK that's sums it up!

When you say Orange block SIP do you know how exactly?

I have so far this morning got Fring loaded onto the E61 and connected to my Asterisk server (itself running on a WRT54GL router) over Orange 3G. Awful calls at first but now I seem to have one leg on GSM and one leg on ULAW and it isn't too bad. I don't seem to be able to force GSM on both legs which would improve things no end.