Dazza:
Wiretwister, for the purpose of this argument, I am ignoring the Lib-Dems, as they, together with all the other parties you mentioned (Scottish/Welsh Nationalists and the Northern Ireland parties) will IMHO never hold the balance of power in this country. You may disagree, but this is a subject close to my heart and I’ve spent many years studying the British political system.
Are you sure about that, Dazza? 
At the moment our system of government relies on one or other party gaining a working majority in order to hold power. If there is a hung Parliament - something which has happened in the past in this country and still does happen on a regular basis in Italy (which has a very similar Electoral system to ours), then the only way that an effective Government can be formed is if a coalition is agreed between one of the major parties and one or more of the minor ones.
In practice, this means that a party such as the Lib-Dems which has a relatively low number of seats in the Commons, can wield a disproportionate amount of power simply by switching allegiances when the need/fancy takes them.
The so-called “First-past-the-post” system of democracy that we have in this country is by no means perfect, but as far as all the systems of government available it is probably the least-worst option, it is very difficult for small parties like bigsidney’s “Truckers party” to get established under FPTP, but the alternatives aren’t without their faults either.
Whilst I agree that the alternatives aren’t flawless, I cannot possibly support a statement claiming that “First-past-the post” is fair.
The current system is based on Constituencies with unequal numbers of voters, largely alloted on a geographical basis. If you compare the figures for seats in the Commons with those proportionally illustrating the way votes were cast, then you will see a rather wild discrepancy. And that alone, IMHO, renders the whole thing undemocratic. 
Proportional Representation has a number of flaws, for a start, the fact that a sizeable chunk of MP’s in a PR system are taken off a party list breaks the constituency link and makes them unaccountable to the public.
Now there I have to agree. 
PR also allows the smaller parties to hold the balance of power and therefore all the policies will have to be “middle ground” and unexciting, this is called “consensus politics”, for consensus read boring.
Point 1…Smaller parties can just as easily hold power under the constituency system, see above.
Point 2…So the wouldn’t the fact that 50% of the public want one thing and 50% want another mean that “consensus politics” might actually be a very sensible way forward? It has to be better and ultimately more democratic than allowing 40% to do what they want and sod everyone else! 
Point 3…Are we to believe that you advocate abandoning the whole idea of a fair and representative government, simply because it would be “boring”!!! 
And I have been…
Oh, I don’t know, Daz. I’ve got some quite strong political views…but I normally make a point of not getting into discussions about them on the forums. The fact that you’ve goaded me into breaking that particular personal rule means that you can’t have sent us all to sleep… 