I made two massive mistakes last year.

My totally reliable and utterly fantastic MK4 Mondeo had to go.

I decided I wanted a new Focus and the Facelift had just come out.
I ended up buying a brand new Focus Titanium 1.5TDCi.
The car has been back 20 times for various issues in it's sub 12 month life and is due to go back again next Tuesday for a few new issues.
Since day one it bogs down, hesitates and generally drives like a pig.
Ford have told me they know about mapping issues with the EGR valve but have no intentions of ever fixing it so I have to live with a pig of a car.
It should also do 90mpg on a run and I have to try really hard to get it above 60mpg.
I've had disgusting customer service from Ford Customer relations and I will NEVER consider owning another Ford.

My Missus again totally reliable and bulletproof KA had a serious case of rot and it was time to let go.

I armed with £2000 of her money decided to play it safe and buy a Citroen C3 from a well regarded local dealer.
It was on an 06 plate with 112k. Full Citroen service history inc a new head gasket and full head rebuild 8 months prior with a bill for nearly £2k.
It was raining however it looked mint. I jacked it up and had a look for any play and all seemed well.
I paid £1800 for it and gave it a proper look over the following weekend. I found a leaky shock, 3rd was whining and the whole one side of the car had been sprayed badly to make matters worse I found all the carpets inside the car utterly drenched.
Took the car back they shrugged their shoulders at the gearbox and told me it wasn't their problem and changed ONE shock.
When I kicked up a fuss about replacing one shock they told me I didn't know what I was talking about and there is absolutely no reason to change suspension parts in pairs.
3 weeks later the release bearing went and put a hole in the side of the gearbox.
Broke the car and lost £1500.