Congratulations on getting Gold Tier. But to get that you must have done several cruises with pando. So surely you dont have to ask this question? We are only sapphire members but have cruised enough to know whats what. From Sunderland by car we can imagine it will only take, depending on traffic about 6 hours. Other transport methods, dont know. But, whatever, all us common lot we dont bite, and you could surely queue with us. We all get on the ship eventually.
There is dedicated check in for gold members and you can check in anytime but I would not leave it later than 4pm. Dont think there is any priority in the carpark queue although I have never found this to be a problem.
Once you've handed over your vehicle to be parked it's then really easy. If you're going from the Mayflower Terminal as you enter the departures area bear left and you will find a check-in area specifically for Gold Tier members. You won't have to get in the long 'post office' type queue like everyone else.
It doesn't matter if you don't get there with everytone else, as long as you're there before the final check-in time that's fine.
I will say that we've used this facility many times and it is much nicer and easier than going through the full 'British' queue situation.