Just had an email from the BGS today which included a link to a new 3D geology map of the UK.
Looks really good and have spent a little while looking at the caving areas on it this evening.
It also overlays boreholes that they have in their records, some of which you can view the reports from, and some that are confidential.
This may be of interest / use to people.

http://mapapps.bgs.ac.uk/geologyofbritain3d/index.html

The 3D viewer overcomes a problem the old 2D viewer had, as it allows the geological mapping to be seen at a greater enlargement. I know this involves the risk of suggesting more precision than the mapping has, but I have found it useful to know roughly where geological boundaries might be on a large scale - I can always check them later on the ground. (For Wales the CCC geological map always allowed greater enlargement.)  The price paid in the 3D viewer is a bit of pixelation.

The degree of transparency can be altered using the tool toggle control on the left hand side (in the old 2D viewer it was permanently onscreen),

.

Interesting

They are started serving the WMS images in a way that they can be used in 3D contexts in browsers (CORS). 

I can now get them working overlaid on survex .3d models in a browser too, 3 counties example here.

Woooo - that's really cool! 
Someday, someone is going to have to write down how to do that...