Which Way East?

I'm currently reading a novel which centres around building a cathedral.  They have just set the centre aisle of the nave by sunrise which made me wonder, do all cathedrals face east? Or, rather, do they face true east?  True in this sense being as near as damn it geographical (ie true) east.

It occured to me that if they didn't bag their sunrise during an equinox then it was either going to be too far north/south depending on the time of the year.

A google search found me this interesting article from British Archaeology (I must be getting old if I'm finding this a good read).  It concurs with my thoughts, as in the 'easts' vary and, as you'd probably except, quite randomly.   There is certainly no link with the alignment of the church and the point of east during the saints day.  However this apparent trend towards more northerly easts in the west side of the country is interesting.

I'm now on the hunt for more info...