Becoming more at home with the 8520 but after returning from Cheshire I now find that GSM not GPRS connects from T Mobile. Alongside the T Mobile is a small triangle which I'm not sure about, but with only GSM I won't be able to get Balckberry Data , will I? E mailed T Mobile but not too hopeful of an early reply. Any solutions please.

Have you tried a battery pull? With the device on, remove the battery for 30-60 seconds then put it back in and let the device reboot.

Stranger and stranger, just switched on again and GPRS is up and the mysterious triangle has disappeared....spoke too soon ...it started to "search for network" and we are back to GSM and the "Bermuda" triangle.What the heck is going on? I'll try the battery pull next.

That would indicate you are roaming. Sounds like a network/tower problem assuming it has worked in that location before.

Yes ,this is home location so worked here before ...is the triangle a roaming symbol? Is it a case of T Mobile sorting it out?

I believe the triangle is roaming; if it worked before it would indicate a T-Mobile problem.
I'd call them Monday and report it.