The following publications are not readily available even in University libraries. If you are willing to pay, the British Library Document Supply service (www.bl.uk) should be able to assist:
Stanton B & G Wignall (1995): Tree Roots: a forseeable nuisance? Solicitors Journal 139 (44) (17 November 1995) pps 1146-1147
Wignall G (1998): Handling subsidence claims: damage by tree roots. Solicitors Journal 142 (22) (5 June 1998) pps 520-521
Wignall G (1999): Tree root subsidence - a working guide. Solicitors Journal 143 (31) (6 August 1999) pps 756-757
Subsidence Guide from Davies Lavery (now part of Kennedy group).
Driscoll R and Skinner H (2007) Subsidence damage to domestic buildings: a guide to good technical practice. BRE Press. ISBN 978 1 86081 977 3 covers more than just tree root activity.
CSIRO (2001): Plant Roots in Drains - Prevention and Cure. (available for download at a small price www.publish.csiro.au). 6 page pamphlet with 4 pages listing recommended minimum distances that a variety of Australian species should be kept from sanitary drains.
NHBCTechnical Standards: www.nhbcbuilder.co.uk/NHBCshop/TechnicalStandards