I'm actually an historic buildings consultant in the UK, but have had a penchant for GIS for years: about 15 years ago, I started using Mapinfo, but only on a pretty basic level. Then I changed companies, where the new company used GGP on a more wide scale, which gave opportunity to play around with it a bit more.
About the time I left this company, Ordnance Survey released their Opendata sets. As a complete integrated mapping of the UK its not great, as they have released in segments and basic formats, and you can either take sections as and when you need it, or use the vectors to create your own versions with your own styles. So over the last couple of years, I have gradually been creating a complete mapping system of the UK based on OSGB 1936, from 1:999,999 to 1:15,000 using this data. replicating Landranger. I have been using a mix of QGIS and ArcGIS Desktop10. I have a full range of maps running in Arc mosaics, but am having more of a problem doing this with QGIS.
Professionally, I use GIS to examine, query and develop various datasets, create and draw maps, etc. and as I work all over the UK, this will be useful in being able to firstly provide easy access to the data which is available, but also in developing a system which is the same coordinate system as the Ordnance Survey National Grid (i.e.OSGB 1936). This is essential, as all the databases I use are mapped in this, and this is the standard for mapping, CAD, etc in the UK - although it is easy enough to transform maps to this, or to reassign the coordinate system for the shapefiles, I need the accuracy of using the right system. So I figured that, whilst it is a fair amount of work, the end result would be worth it in the long run (and yep, Im happy with it!).