1.) What costs are involved and is it possible to make any money to suvive from it?
It depends on how you do it. There are some part sponsored schemes out there which you can do a search for. These are hugely competitive. If going it alone, expect costs between £35000 and £120000 depending on how you want to do it (modular vs integrated thread at the top).
2.) Has anyone done it? could you please tell me about your experiences?
I trained modularly, worked very hard, got good pass marks in theory exams and first time passes in practicals. I was (relatively) lucky and got a job flying piston twins soon after getting my licence and after over a year of that got a job in a commercial airline.
3.) does it help to get into commercial?
I'm not 100% sure what you mean. If you want to know if it helps to get a commercial licence to do it for a living, then it is almost a necessity as apart from a couple of scenarios you are not allowed to earn money without a CPL. If you mean does it help to fly commercially (airlines etc) over general aviation flying in order to earn a living, then in general yes, because although there are some well paid GA jobs out there, there are less of them and you tend to need experience to get them.
4.) is it who you know and whether you have rich parents, or can a standard young adventurous but determined individual do it?
Who you know is a very large part in getting started. Once you have experience it is less important but still plays a big part. Rich parents, well.... if you mean rich and high status to try to get you a job then it helps in a lot of countries outside of Europe, inside Europe less so but it still happens.
5.) Grades! i am currently studying at 6form, but have never excelled in education, i have 8 GCSE'S and a C in english and maths ( not science ) and am struggling through A levels... ?
Good grades are not required except they will help if you are looking for part sponsored/mentored schemes. A decent understanding of GCSE level maths, and to a lesser degree perhaps physics will ease the theory exams a bit, but you don't need to be brilliantly smart to pass them.
5.) any others things you would recommend!
Do a lot of research, speak to as many people as you can, think about it long and hard and consider all your options. It is a big amount of money to spend and the chances of getting a job afterwards are on the slim side.