No such thing as DPF on a Td5, Eu3 modells have a "passive" catalyst on the exhaust pipe which the best move is to be removed cos all it does on such old vehicles is to restrict the flow nothing else and i doubt that somebody is so scrupulous to replace it with new
https://www.lrdirect.com/wcd000500-front-pipe-ds2-td5-catalyst ... as about MOT, an old and clogged one would increase the nox instead of reducing it that's a verified fact