It is proposed that the CAA gets £534 for each test that is carried out by a CAA Authorised examiner. Then the examiner charges an 'appropriate' fee determined by each examiner, PLUS they will be allowed to charge expenses.
AND the CAA will allocate the examiner who is to carry out your test and you will not be allowed to change him/her.
Rumour has it, if you do not do the test due weather, sickness, technical issues, etc you will still have to have the same examiner - when he/she is next available.
In summary, if you get an examiner who charges, say, £400 plus high expenses it will cost you a lot more than £800 and you will be able to do nothing about it.