The 1.8TD is a very basic engine, so adding an ECU shouldn't be hard.
I think though that aftermarket common rail ECU's are quite pricey (not looked into it too much though).
Maybe look into fitting the 1.9TD engine from a Peugeot?
Always been a better lump, although you'd have to try source a gearbox from an LDV van with the 1.9D/TD engine as it was the only car/van avalible with this engine and RWD.
The 1.9TD engine can be tuned easilly to 120bhp+ with an FMIC and some pump tweeks and if you fit a bosch fuel pump can be run on 100% vegtable oil