Be aware that the results include many duplicates (e.g. different faculties at Glasgow, and the STACK maths system seems to link from 3 different URLS) but also that it doesn't include every Moodle in UK HE e.g. it doesn't find this site at Strathclyde University:
http://neo.ces.strath.ac.uk/moodle/
That query was designed to avoid false positives, i.e. point to nothing but Moodle sites, even if it missed a few Moodles, but another revealing search query is this:
This search relies on the observation that because of Moodle's catchy branding, many users seem to include that name in the url. Bear in mind that these are not all Moodle sites, though all are web pages that refer to Moodle in some way (JISC user mailing lists etc.) which is interesting data in itself.
The big campus wide adopters in UK HE are Glasgow and Goldsmiths (which someone else linked to above), at least as far as I am aware, but you might also be interested in looking at Dublin City University in Ireland who have some good documentation online about their choice of Moodle.