Hello Andrew,
My money would be spent on getting the injectors checked. The unburnt diesel smell would point me in that direction. Probably not a pleasant vehicle to be around! I take it the fuel filter has been replaced to schedule with a good quality unit - not that it is likely to improve anything with your symptoms on its own, but it is always good practice to reduce the chances of such problems. You could try some injector cleaner in with the fuel since the cost would be minimal and it might - just might - improve the situation.
Good luck with getting it sorted.
Kind regards,
Gareth.