If Paul used XAPI to extract a part of the country in order to build his Garmin map then it's possible that his XAPI excerpt isn't complete. I've been seeing more and more of this happening in South Wales where I'm doing exactly that.
It seems (from other comments here) that there's a known problem with the various XAPI servers occasionally dropping a minute-diff and never recovering. I've seen this happening since the switch to the 0.6 API: I had never noticed it before that.
I've been sent on bogus routes around Swansea (my home town) due to small bits of roads going missing. I've got a partially missing westbound carriageway on a dual carriageway in one particular case, I've also spotted a missing urban one-way street and a few other cases.
If Paul looks carefully, does he spot (on the Garmin) a missing slip-road on a roundabout, responsible for there being no valid route from one side of a dual carriageway? Worse is an apparently present slip-road on a dual carriageway where the 'oneway' once pointed the wrong way, but has been fixed on OSM at some point, but where the fix was part of a minute-diff that the XAPI server dropped?
I thought that XAPI was totally buggered at the moment. I haven't been able to use it for weeks (months?) I am currently using: http://download.geofabrik.de/osm/europe/great_britain.osm.bz2 Cheers, Mark