As I said in my first preview posting, there are very few districts where there is a true three-way race (I've seen lately, the neologism--new word--for it is a "truel", or three-way duel). But I did find some.
Out of the 650 constituencies, I identified the one which appeared most like the national percentages in the 2005 election, and, to make things a bit more valuable for projection purposes, the boundaries of the district were not changed.
The constituency is called Pendle: it is in the county of Lancashire, in the northwest of England. It is a somewhat rural area near a heavily-populated strip, (near Manchester, Burnley, Blackburn). It is most known for a witchcraft trial in 1612, in which 10 were hanged (what, no burnings?)
The 2005 percentages (from electoralcalculus.co.uk): Labour 37.1%; Conservative 31.8%; Liberal 23.2; Other 8.0%. The projections, from the same source: Conservatives 35.1%, Liberal 27.9%, Labour 26.7%, Other 10.4. These projections are very, very close to those I'm seeing for the national popular vote.
The idea of looking at such a bellwether is to see whether the national opinion shifts are fully reflected in such a race (as opposed to, say, the Liberal Democrats improving a lot in districts where they have no chance to win, of which there are many). A theory that I subscribe somewhat to is that they may actually improve more in such a race--but remember that Labour has the incumbent.
I saw that the Pendle Council is offering to shoot out its results on Twitter and Facebook this year, so I've "friended" them, and will be looking for some results on Thursday.
If you don't like my choice of Pendle, here are some other three-sided constituency races worth looking at: Blackburn, Bristol Northwest, Leeds NorthEast, Northampton North, and especially Watford and Ealing Central and Acton.