Service blocked means that you do not have the proper plan from your carrier. Contact Orange UK, they haven't set you up correctly.
You still have the BIS plan so PIN should work and you would work while wired to the BES via USB.
If you contact RIM they check your plan from the carrier and from there you can be sure that Orange UK didn't set you up correctly.
I used to contact the carrier with the customer on hold to ensure that the plan would be updated correctly or at least get them to see their error. It's not a required thing at RIM but I would rather spend 10 minutes on hold at Orange then have a customer get bounced around by their carrier.
Just ask the rep at RIM to contact the carrier while you wait on hold. You could also be paying for the plan but not actually have it, from what I understand they are 2 different systems.
One is billing and the other is called Provisioning. I know that some carriers do not allow reps access to Provisioning so they look at billing and tell you that you have the right plan even though you're actually provisioned for it.
Keep pushing the carrier and you'll get everything straightened out.