Will try the sim cards tomorrow as I have no mobile coverage at my house to test but this could certainly make a difference.
Have just tried changing it to UMTS EU GENERIC/UMTS and it accepts it however the AT&T Software wont work it just keeps connecting and disconnecting the modem/adapter in the device manager, I would think I would need some other connection manager to connect to the EU GENERIC firmware,
Every time I load on the AT&T software it loads on North America UMTS firmware however when its set to this I can get a signal on all uk carriers and it does connect but only for about 2 mins and it disconnects.
Also tried changing the firmware to the following-
1.T-MOBILE UMTS with my uk EE network sim wich is UK T-mobile and orange
2.Orange UMTS with my EE sim.
3.Vodafone UMTS with my Vodafone UK sim.