What does the extended project actually mean?The EPQ is a qualification you get, equivalent to an AS-level, where you research a topic you feel passionate about and produce a 'product' (such as a peice of music) and a 1,000 word essay/report type thing or a 5,000 word report, based on your findings.
How is it written and how long time period + number of pages are needed?Well, you fill in a log book of all your progress and write the aforementioned essay. Most students do the bulk of the EPQ work in the summer holidays, then finalise things when they get back to college.
Who marks it and what are the marks allocations/grade/etc.?Not sure who marks it. It might be your tutor, then it may have to be sent off for moderation by the exam board. The grades range from U-A* and they carry a few UCAS points.
What are the benefits of doing the extended project? e.g. any UCAS points?It shows your willing to undertake a project off your own back and not do work you have to with your normal A-levels. It's meant to be quite 'fun' when you get your teeth into it.. Universities like to see it because it prepares you well for University study, but you probably won't be made an offer on your final grade.
What subjects can you do them for?What topics can you pick from?Can you only do it in subjects you're doing for A level?You can do it on whatever topic you want. It doesn't have to be related to your A-level choices, but general one will chose something related to what they wish to study at University. You have to boil the idea down to a single question at the end, however.
Can you enter yourself or does the school have to enter you?Not sure. Just do it with your school, it's much easier