I haven't applied to EZY since they've not been particularly clear about their loan guarantee options and I resent the fact that they make you pay for the assessment. Been there done that with a different programme and didn't think it was great value for money, though each to their own.
However, having been to Dibden there are probably a couple of things I can mention.
Getting there is a pain, I stayed at a local B&B which I would recommend but bear in mind that a taxi to Southampton Central station is about £25. There is apparently a ferry that takes you right to the middle of Southampton but I didn't use it since it was dark and I was knackered, just wanted to get home.
I passed everything except one of the two the group exercises. I tried to involve someone else in the group who was a bit quiet but it looked like I was trying to put them on the spot. So play it cautious and don't try too hard, you'll likely also have more than one wanting to be the time-keeper.
Maths I straightforward so long as you revise your pen and paper arithmetic for half-an-hour per day, you should all aim for 15/15 on this one.
Aptitude tests will vary from person to person but bear in mind they are looking at how quickly you can learn. Aim to improve your score on each of the three attempts.
The interview I didn't find too bad, though it seemed like those with quite a bit of life/work experience would find it easier than those straight out of school. Not too bad compared to final-stage interviews in the train driving world, trust me, those are hard!