As far as I'm aware, there has never been a 1.8 diesel in the Octavia. If it's a DPF diesel, then it'll be either a 1.6 or 2.0.

The 1.6 diesel is notorious for problems. The 2.0 is better. Though that's a bit like saying having to eat 1 slug is better than having to eat 2 of them !

Technically, in law, you can reject a car up to 6 months after purchase, and receive a refund - though the garage is entitled to make a 'reasonable deduction' for the use you've had of the car.

The problems are if the garage refuses to accept your rejection, or the amount of deduction is in dispute : you'd be left without the use of a car (you've rejected it, so using it weakens your argument that it wasn't fit for use), and you'd have to go through the courts to get your money back. All of which takes time, and you've not got the use of a car whilst it is ongoing.

Finally, the older (or cheaper) the car, the less your legal rights are. It comes down to what your 'reasonable expectations' of the car were, bearing in mind the age and price paid.

In short, it's quite messy - especially as you've left it so long before thinking about rejecting the car. If you'd decided to reject within the first 4 weeks, the legal position would be a lot clearer, your rights really well defined.

I'd probably suggest trying to find a new DPF and getting it fitted for less. £2,000 seems ridiculously expensive. Or you could try getting the DPF cleaned out (properly, rather than a bodge job !) by the 'ceramex' process - a google search my help you find someone relatively local to you.

A local garage have flushed it numerous times but the problem persists.

Flushing out a DPF does not work, its an urban myth propogated by YouTube and other sites, its also illegal if any residue is simply flushed down the public drains. The soot particles are chemically bonded to the matrix inside the DPF and buring them off at high temperature is the only way to remove them, this is what a regen does. Some companies offer a process where the DPF is heated up and compressed air blasted through the matrix but it takes many hours and there is no garantee it will work, its maily used on comercials.

Once the light comes on the dsh solid it normally means the DPF is blocked which means replacement. Aftermarket ones are available from companies such as BM atalysts at a fraction of manufacturers prices so don't take the first quote you get.