If you own a vehicle with an ICE, 2 things you should know.
Get yourself an OBD II reader/scanner, mine was 30 quid from Ebay including postage, there are better ones but I guarantee if yours develops a fault it will save you far more than the cost the first time you use it.
If you get a fault, scan the car, make a note of the fault codes, reset and wait and see if they return, often they will not, this is all any breakdown service will do, and why the small print says you cannot call again for the same fault. Then use Google, often they can be easily rectified yourself, there are forums and video for just about every regular fault on any vehicle on the net.
If it returns and there is no easy fix, you know the faults before it goes to the garage, if they tell you there are other things wrong, you know there is not, sometimes one fault code is caused by another, fixing the easiest first often cures them all.
The biggest cause of faults is a low battery, it can cause a multitude of faults including stopping an automatic gearbox to stop working, if your car starts developing regular faults, change the battery for a new one before anything else. Sensors and control units are extremely voltage sensitive. Also check alternator output.
Often a new battery and reset of fault codes will solve a whole heap of problems.
NEVER GO TO KWIKFIT OR HALFORDS, EVER. I could tell you hundreds of horror stories.
Before buying any car, use said internet forums and Google, there will be information even on the newest models, pros and cons, even if it is only road tests but if it uses engines used before, a mine of information on regular problems.
Always use a very good car check company, not just HPI, many cars are repaired and not recorded for one reason or another, it will tell you every time the car has been sold, and if it was sold by a salvage company, often showing pictures of the damage.
This video may be on an old vehicle, I found it because mine had this problem caused by a flat battery, but it gives you an idea of how a scanner and the internet can save you time and money, how many of these went to a main agent with this problem ?
External Link/Members OnlyI had to collect one from a customer of Ford yesterday, the owner found a picture of it badly damaged, they had to return his money, plus a bit more no doubt, because they had not done the relevant and available checks.