1) You could occasional run some premium diesel through the system - I do occasionally although it is a fair bit more expensive.
2) Drive it slightly more like a petrol car and keep the revs just a bit more higher i.e. I keep mine in 3rd in 30 zones (6 speed box) and the car feels more comfortable. This maintains heat, heat cleans up carbon and the DPF
3) If preferred stick in some Diesel Reddex from time to time.
4) The Forte fuel additives/cleaners are highly rated in the trade.
If it's an older Diesel engine it maybe worth removing the injectors and have them professionally cleaned and checked for spray pattern. Plenty of postal services available or a local diesel specialist can do them for you.
Thanks guys. I put the redex in it. It’s a 2011. Seems to be quite good on the diesel. Would yous know if it’s a timing belt or chain that’s on it? Read that some have belts & others have chains but can’t seen to find which it has. Accidentally put £40 of petrol in it this morning. Luckily enough I drove it home (200 yards) from the garage to realise what I’d done. Few hours with a syphon pump & another £40 down and a days wage & it’s fine thankfully. Will not do that again