I used the one from the Motorway Police link.
I agree you have to be careful but you would hope the NWMP would give good info.
Mark
You'd hope that DVLA/DVSA would give accurate motoring info but they don't always - what's worse is that when an error creeps in it can take them years of complaints from "anoraks" to get the website corrected.
eg - From 1997 to 2013 anyone passing their car test was limited to towing an outfit of 3500 kg total, as now, but were also limited to towing a trailer less than 100% of the car's kerbweight - this 100% restriction was withdrawn with the 2013 revisions but it took 2 years of complaints to DVLA to get them to remove it from the website, partly because they argued they were right but had to back down in the end.
There's no guaranteed source of motoring law on the internet - the nearest you'll get is Stones' Justices Manual in courts and public libraries - but even magistrates and solicitors find it hard going!