Is anyone using such a phone, and what would be the cheapest I can buy which allows a T-mobile sim? I've only just discovered this capability, which is on the new HTC HD2 Smartphone whose spec can be found here
HTC HD2 - Smartphone - WCDMA (UMTS) / GSM - 99HJY002-00 at Insight UK
Don't trust a retailer willing to sell you a bike without a bell; if they are prepared to skimp on this basic legal requirement, think what they'll resort to if things go wrong.