The CJA does not apply to anything that is licensed. The case was lost but there is an appeal pending and as we go to print it's looking good. Keep yer fingers x'd. This one has taken over a year. The PA was returned after a long time, as it was seized and kept as evidence.
Police can set up road checks when they believe there is a Breach of the Peace, or one is imminent.
Although they can be asked for reasons, and might later have to justify their actions, they may turn you back from your destination. If you fail to comply, or you come back, you can be arrested and you are committing an offence. The important thing to remember about section 63 is that it applies equally to places that are NOT trespassed. It's worth remembering that the blocks can be in the middle of the country and a long queue of cars is not what they want. Don't give up, don't go home, there's safety in numbers, and the persistent and sorted get there in the end.