I found this a bit earlier (actually, from a news link at the RH side of a Voxalot page)
N95 VOIP crippling caught on camera; can carriers evolve? - SlashGear
I don't imagine that Orange UK are alone in this practice.
There is a thread about this on the Truphone forum, where I've speculated on whether having the phone reset by a Nokia service agent could lead to a potential warranty dispute with the network about a later unrelated fault
Does your N95 have internet telephony disabled? - Mobile VoIP Forum
off-topic - Truphone uses it's own installed client, and so far does not reveal SIP settings, so would not be compatible with Voxalot