Bit late tonight to look it up, and check the exact facts but there is a precedent for this. Patrick Gordan-Walker (??) lost his seat in Smethick (??) 1964 he was made a Minister, but there is a time limit on how long a Minister can act wihout a seat in one of the two houses of Parliament, P Gorden-Walker was put up as a candidate for Leyton or Leytonstone in East London, and lost that too.
I think you will find that Alex Douglas-Hume resigned his peerage and was made Prime Minister (In thoses days the queen was "advised" to send for the chosen Party Leader) befoe he was elected for one of the Northern Scotish seats in 1963.
On a more specific point, my personal judgement is that Howard has been chosen to do a holding job untill after the General Election in 2005/6, and thence in the aftermath of that defeat then Portillo, Davis and others will fight it out.
Mind you I could be wrong.
Certainly there is a Labour Vote to be squeezed in the Folkstone Constituency of Howards, and if a deal was done between, say Canterbury, where there is a substantial Liberal vote to be squeezed thhe reesulting election could be "interesting". Expected boundary changes in Kent might confuse the issue
'Catter "anoraks" are invited to Click 'Ere where the facts and figures are stored, and all reasonable answers can be found. Scroll down untill you find the election figures you need.