The DPF on the D5 motors works in a totally different manner to conventional DPFs. Not only that, they're about twice the volume, so they don't get blocked.
To really cheer up owners they're a dry system, with no nasty EOYLS type exhaust additives system, so 95% of equipment that causes hassle on a typical DPF car simply isn't fitted on the D5.
As Boney says, they simply don't cause problems on a D5 unless the car has been seriously, grossly, nastily abused - forget everything you know about DPFs when buying a D5 as it simply doesn't apply.
I've had a P3 D5 185 and it was swift, long legged, and moderately economical. It shares the platform with Ford products - that doesn't mean it shares the same floorpan, it means key dimensions such as engine mounts, door hinges, suspension pick up points, etc, share the same relationship in 3D space. This means they can be built on the same line or, in Fords case, they saved money by duplicating the same line in Gothenberg. It also means engines can be swapped between models without ennecessary engineering required for the conversion, enabling Ford to steal the 5 cylinder units for their cars, and other items such as supension arms etc to be common across many models. Thus it's a platform, and not a shared floorpan as might have happened in the old days - the sheet metal underneath is not common, and while related it is most definitely not a Mondeo with a different body.
The biggest issue with P3s is electric gremlins and mine was afflicted. I got to the bottom of it in the end but the average buyer would have to pay a garage, and due to the nature of the car it'd need to be a marque specialist or a dealer, which can be spendy. Buy one by all means, but buy wisely.
The P2 is probably the better ownership proposition in the that regard, the downsides being there aren't many sweet low milers left, it's not quite as sharp to drive as the P3, and the P2 engine isn't as lively as the more powerful 185/200/210 units the P3 could be had with.
Addressing the OPs question directly, £10k is a curious price point. Unlike even 5 years ago that doesn't buy you a lot. For anything of any serious size or capacity £10k is going to buy to at least half a decade plus and lord knows how many miles of previous owners abuse, cheap servicing at Kwap Fit, budget tyres, etc, to the point where us saying "such and such car is a good bet" is a moot point.
At that lower end of the market you're probably better off buying on condition and history rather than any notional idea that the Ford Tippex is the idea car for you.