Original post but can't create a clickable URL:
https://www.reddit.com/r/CarTalkUK/s/RMYqZTOV8W

Hi everyone, thanks for your patience on this.

So, after finally being forwarded to my bank to help with the matter, I have an outcome.

The bank accepted liability (due to the finance) and they have recently said they'll take the car back + offer me £550 compensation for "loss of enjoyment". Because I paid £1000 directly to the dealership to reserve the car I won't be seeing that money again, and they have evaded punishment by the sounds of it unless the bank or Trading Standards have conducted an investigation. I'll never know.

The bank said they'll repair the car providing it is financially viable.
Cost: £4,670 to replace the DPF and a few sensors and components to accompany.
The bank have refused to repair it on the basis that they have only valued the car at £6,000... No mention of this value previously, even though I told them I bought it for £9500. They'll contribute £3000 if I foot the rest but that doesn't seem financially viable to me.

So.. options:

1) Return the car, receive £550 comp and accept a £1,000 loss of deposit. Lesson learned.
2) Foot £1,670 for the shortfall, plus a ~£300 BMW service (overdue due to not being sure I'd keep the car).
3) Raise it to the Ombudsman and see if I can have the car's value increased, or my direct deposit clawed back somehow. But I'm not sure if this will remove my right to accept the current offer to take the car back if I fail with that claim.
*4) Keep the car. I'm already invested, get a few sly MOT's and otherwise keep it BMW Approved stamped so I can retain some reasonable value for the target market that go for cars with deletes. I intend to keep a vehicle for 3+ years, or until the wheels fall off.
*The flex pipe has leaked some more so I'll need to get a new one eventually. The exhaust noise has increased a bit but isn't anywhere near being antisocial yet.

Do you recommend I cut my losses and return it, or keep it now with the EGR/DPF delete?

If I bought another car I would definitely get something smaller/cheaper to offset the loss of the deposit.

Update: Dealership refusing to fix car