Fees in advance?

In a recent exchange of correspondence, I sought a breakdown of fees from an HCEO.  This company provided the figures very promptly, but included a number of charges for actions I did not believe had yet been taken.  When I queried these, I was informed that the bill included items which typically would be charged during a levy of execution- but which might not arise in this case- and which would be removed from the account, as appropriate, as matters developed.

Does this seem right?  Does it seem fair?  Is it clear and transparent?  How does a judgment debtor know what s/he is required to pay to discharge the execution? 

Let us imagine (for the sake of argument) that the director of a large HCEO company- let's say John Marston of Marston's Group purely for example- takes his Jaguar to the garage for a service.  How would John react if he was, upon delivery of the car, presented with a bill by the mechanics for a range of major repairs- replacing all the tyres and brake pads, replacing various electronic components, some major bodywork and respraying- because this work often has to be carried out on vehicles and it might need to be done on his?  All he has to do is pay now, in advance- but there'll be a refund or adjustment later if it turns out that none of this is necessary.  Would John accept this outrageous and speculative imposition?  Would he pay and trust the garage- or would he decide to go elsewhere?

How can consumers of any service (willing or unwilling) properly be charged for actions which have not been performed and may never be performed, as they are contingent on circumstances?  Payment in advance is reasonable enough if you can be confident that what you are paying for is definitely going to be done; however, if the charges are dependent upon there being seizable goods, upon access to those goods and upon a range of other unpredictable factors, it seems to me that such demands should not be made.

It will (hopefully) be little surprise to hear that the courts have agreed over the years.  A bailiff should only charge for what he has actually done; that's the rule, in a nutshell, and a pretty sensible and obvious one it seems.  Advance, speculative- or even wholly made up fees- should never be included on accounts.  But, clearly, they are- and it isn't just this particular firm either.