Although Champion have correctly deducted Income Tax and National Insurance contributions from your gross earnings, it is possible that you can claim a rebate for the travel & subsistence costs you incurred during the 2016/17 tax year.
If you have been deemed to pass the Champion Supervision, Direction & Control (SDC) tests, and have subsequently confirmed to Champion that there was no further change to your working conditions, then it may be prudent to submit an SATR.
Note – if your travel & subsistence claims are less than £2,500 in 2016/17, the need for an SATR is replaced by the submission of a P87 form.