When I did the Cobham interview, it was similar to other airline interviews involving a series of group tasks which take about 20 minutes each. The tasks can be intense, and a couple of recruiters will stand behind or walk around the group watching everybody's contribution and taking notes the whole time. You will quickly forget they're there, though, as you immerse yourself in each group task. Just have lots of fun in each task and you won't feel stressed at all. Smile the whole day no matter how tired you feel.
During each task, make sure you don't say too much, or say too little. There are usually no right or wrong answers to the tasks; the recruitment team are simply looking to see how well you interact with others at your table, and for each task you will move around and be with different people each time. Don't latch on to another person (in case they get the boot), but don't be aloof.
Never get into an argument with another candidate during a task, and try to include others in the group who are a little quiet. Aim for complete diplomacy. The recruiters will weed out those who are aggressive, or are too quiet - they are looking for confident, assertive people to fill the role. Cobham are very good at not discriminating on age, sexuality or gender.
Regarding dress, go for the more conservative heels. Aim to look handsome, not flashy. Make sure your dress goes below your knees. Wear your hair in a bun if it's longer than 30cm, but however you tie your hair, use tortoiseshell to cover elastic bands, and hide any bobby pins. Also wear sheer or support black stockings.
Regarding jewellery, wear pearls or diamond earrings only, just one ring on each finger of silver or gold, avoiding coloured stones. Make sure you wear a watch, but it should have a silver, black, brown or gold band.
That should get you through the interview, if you can remember all the above! Lol. Good luck!