This forum will provide you with a wealth of information on every possible topic that you could think of relating to attaining your dream... so have a good read from time to time.
The above advice on the medical is sound. You cannot possibly know all the ins and outs of your own body and the Class 1 will tell you if you are medically fit to do the job. People can go on for years without realising that they are slightly colour blind, for example. It costs £310 and is done at Gatwick.
Good financial planning is essential, also. Thoroughly research all the available routes to the right-hand seat, and don't, for God's sake, expect you are owed a jet job as soon as you have a CPL/IR/MCC.
Be flexible, work hard, be pro-active, seek out and accept good advice, keep busy with flying and do well in your BTEC and you'll be stood in good stead.