The lockers need a £2 coin each. And the first locker I used swallowed one and I didn't have a spare coin, so I'd take 3 x £2 coins if you want to use 2 lockers. (Annoyingly customer services were happy to give me the £2 back but only in £1 coins as they didn't have any £2 coins
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They open the bit with buildings built from lego about 9.30 so get there to 'do' that bit before queuing up by the entrance to the rest of the park at 10 when it opens so you will be a long way ahead of people turning up at the entrance at 10 iyswim.
If you are desperate to get on one ride it is worth doing the one shot jump the queue purchase- think it was £8 per person. Better than the queuebot where if the queue is 90 mins you still have to wait 90 mins, just not in the queue.
DS most liked Laser Raiders, followed by the dragon coaster, pirate falls and river splash. He wasn't keen on ninjango (which had the longest queue on the day) as it didn't really work that well. It missed a lot of 'hits' and I think you have to be sitting just right and at just the right height to register properly.
Splash zone great to run off some energy and muck about without a queue, don't know if the weather will be up to it on Friday, but it its a possibility take towels and swim gear or change of clothes.
Food is mostly crap so you are better with a picnic, but again, this is weather dependant.
If you've got the energy it really empties out last 40 mins or so, so you can often get on the ride that has alluded you due to queue size all day.