As Darren has posted, usually they berth at the P&O ferry terminal, although other quays have been used in the past with a large marquee set up. Unfortunately most arrivals are in the early morning hours and departures usually later in the evening.
Where possible I have ventured to the small village of Paull to the east of Hull to get them arriving as I find the security arrangements at the lock restrictive for good photos. However this wouldn't be an option for you on foot
Used to be a lot better as seen http://www.shipspotting.com/gallery/photo.php?lid=2611763