My mistake. I saw the ".com" and assumed it was a US site since you UK folks usually use "co.uk" (and you're right, I didn't even catch that I downloaded it from miui.us).
Thanks for the feedback, anyway...I'll try it out.
I'm running MIUI v4 2.7.6 (downloaded from: http://forums.miui.us/showthread.php?17792-%28Official%29-MIUI-us-V4-2-1-20-%28-03-22-2012-%29-Working-Phone-Data-MMS-Stock-Camera&p=73489#post73489) on my Motorola Droid X (Shadow).
It works great, except that I have a persistent "No service" message...