Most companies train their apprentices to A License standard (mine does) Assuming you continue working hands-on in the industry, to progress to B1/B2 level will involve fulfilling the experience criteria (which will basically involve recording the details of the work you have carried out as part of your job) You will also have to pass the relevant exams. The only possible cost to you will be CAA exam fees (although a lot of companies pay for these anyway) Should you choose to attend course/s to prepare you for the exams there may also be cost (but Virgin have an excellent training school and may give you courses for free!)
Hope this helps