Here is how to avoid extra charges on your MOT and few tips for preparing for one.

Before taking your car in, do your own little checks and all the things you should be doing regularly.

1. Do a road test by driving for a while paying attention to any issues, sounds during ignition, sounds during gear changes / acceleration / braking, any veering / listing in either direction when driving straight and be honest with garage over anything unusual. They can just hook a machine up to your car to get information but it is better safe than sorry.
2. Check your tyres yourself for wear weeks before MOT. Replace any that are goosed and this allows you to choose brand and can be cheaper than having tyres replaced by MOT garage.
3. Put your tyres to exactly what pressure they should be on your door label, as close to MOT day as possible. You should be doing this regularly anyway.
4. Check your wipers and replace any that are frayed or leaving streaks. This allows you to choose brand and can be cheaper than having wiper replaced as part of MOT. Also take five minutes to watch a YouTube video on how to replace wipers instead of paying £3 each for Halfords to fit them.
5. Check your washer fluid and fill to MAX the day before the MOT.
6. Check all bulbs and lights are working, also note that some electrical issues in a car can be fixed with a simple change of fuse of which you can buy hundreds on Amazon for a fiver. Then watch a YouTube video on where your fuse box is.
7. Ensure car is completely empty before MOT, doesn't need to valeted but just keep it empty. This includes removing all air fresheners from mirror, Sat Nav holders, etc.
8. Remember to check you have been given back your locking wheel nuts if your car has them BEFORE leaving garage.

Not all garages are scammers but I am convinced that the ones that are tend to scam more with people who poorly maintain their cars as they are more likely to have no clue about their car's condition.

So if you have taken care of the things above, it may send a signal you are well aware of the state your vehicle is in and will call them on their bullshit but at the very least it gives you the freedom to choose your brands and companies to get the usual MOT type charges fixed.

On the way home, pop in for a quick wash / valet since your car is empty anyway and then drive home safe in the knowledge your car is fine and feels brand new.