chances are you need a fuel drain, or just had one if you are reading this.
the cost of a fuel drain from an independent fuel draining company is between £145 & £250, the price depends on
1) distance from drainer
2) type of car (some cars require more complex drains such as volvo xc90 or twin tankd BMW’s & Mercedes, some Audi’s etc
3) whether the car has been driven on the wrong fuel and needs a fuel system flush, which is a straightforward procedure but tankes longer than just draining the tank.
the time of day or night does not really come into it, unless its a very unsocial hour, weekends, public holidays etc are all the same as a normal weekday.
a dealer may charge £4000 to £9000 for major fuel system and engine rebuilding, which in my opinion is mostly unnecessary.
The AA does do fuel drains and have a fleet of mobile fuel draining vans, they do charge members and cost about £230, they are quite often very busy and have long waiting period
The RAC have a few fuel draining vans but I havent seen many in the south east, they used to sub contract out most of their jobs to garages and fuel draining companies.
some dealerships will charge between 400 and 800 for a drain that does not involve pulling the engine to bits, but for some reason they often say they will take the tank off and swill it out.
your friendly local garage will charge the same as a fuel draining company, but you normally have to get the car to them
and of course you can do one yourself, or get a mechanically minded friend to help out.