Loopy, assuming you are working for easyJet (not very clear by your thread title!!)
The 10 point drill MUST BE KNOWN WORD FOR WORD - If you don't know it word for word, you will lose points on your SEP exam and could be offloaded from flights at the briefing stage.
The 15 drill is not a drill, it's your 15 points of cabin secure. You don't need to know this word for word, but you do need to know all 15 points and write them with the correct information. For example "Overhead lockers fastened securely" could be written as "Overhead lockers shut properly" and would be a pass, but "Overhead lockers shut" would be a fail.
Airport codes you do need to know, because you need to know where you are flying to on a daily basis. It is rather annoying when people keep saying "Oh, where is MJV? is that somewhere new? What country is MJV in?" etc
With regards to easyGroup companies, well there are not that many, so you shouldn't really have a problem remembering them. Just remember the company names "easyMobile, easy4Men, easyBus etc" but not what they actually do - because the name should be enough to tell you.