The 90 has a different Turbo than the earlier TDDi 115's (fixed vane as opposed to variable vane). In late 2001 they changed the 115 TDDi over to a fixed vane Turbo also when the TDCi 130 was released (not sure why - probably cost cutting or could be because the subsequently released TDCi 115 had a fixed vane turbo).
Not sure if anything other than the ECU mapping is different on them. There are not that many in the UK anyway as it wasnt really offered here - though there are a few UK supplied cars about which were probably supplied as a fleet to companies wanting to save a bit of cash.