Options Regarding Possible Faulty Car VAUXHALL Grandland X (A18) (06.2017 - ...)

I part exchanged an astra for a grandland back in July 2023.

The car was not one they had on website but at dealership they said they had it in recently and not yet up.

I only part exchanged due to gear box on astra went took it to a local garage paid him for new gear box and turned out he made a bigger mess after I took to vauxhall for inspection turned out would cost £4000 to repair.

Anyways the grandland has had nothing but problems since purchase. I have taken it back on 5 occasions since purchase for various things.

good thing I took out extended warranty!

1) Washer motor and pump replacement required -November 2023

Following replaced on May 2024 by Vauxhall

2) O2 sensor required replacement

3) gearbox required replacement

4) Engine required replacing due to metal fragments in oil

One year on i understand general wear and tear no problem but the cost during service and MOT has mounted astronomical for even things like auxiliary belt and wet belt requires changing ? doesn’t this get changed if engine is replaced ? a mechanic told me this so not sure why they advising this when the new engine is only a year old.

Milage is 60,000 but 5000 only on new engine.

Am I in my right to question and complain about these costs ? I have raised it to motor ombudsman last year as they magically priced the car at £15,000 originally then all these faults have just kept coming so no way should the car of been this price when a newer model by a year same car in white was priced at £12,500 4 months after I purchased.

Just need some help and guidance please