Here are some updates to the current Road-Railer fleet lists and the OTP2003 book.

Elec-track Installations

These are both in the book (p142), albeit without road registrations.
ETI60 - GD02 UKL - Mercedes-Benz Unimog U400 with access platform - 195945
ETI?? - GL52 LWL - Mercedes-Benz Unimog U400 with access platform - 201626

Hydrex RSD

4142 - Rexquote/Fiat Hitachi EX135W - MA00000358 - not in 2003 book
4154 - Rexquote/Case 988P Mega Railer - CGG0232325, RQ1641 - not in 2003
4155 - Rexquote/Case 988P Mega Railer - CGG0232324, RQ1628 - not in 2003

Nor Ex Hire (Rail)

D03 - Barford SXR6000 swivel skip dumper - SX60545 SMNE0265 - not in 2003
GEN10 - Genie Z-45/22 Self Propelled Boom - 006486

Readypower

FR619 - Rexquote/Case 988P Mega Railer - CGG0232314 - not in 2003