Answering Ian ( again ) : Why are the UK carriers conventionally powered?

My friend Ian always has good questions for me after reading Definitive Lapse of Reason.
He did first out of this Post :
http://definitivelapseofreason.com/2013/01/26/the-definitive-top-ten-list-of-marvels-of-nature-and-the-universe/

which earned him these two answering ones:
http://definitivelapseofreason.com/2013/01/31/readers-question-are-stars-alive/
http://definitivelapseofreason.com/2013/02/06/readers-question-would-we-even-recognize-alien-life-forms-science-fiction-answers/

Well, he’s done it again ( No Oops, all fine by me! 😀 ) after checking out my 2 part piece on aircraft carriers and possible WWIII :
http://definitivelapseofreason.com/2013/08/11/4-aircraft-carriers-in-the-news-and-the-next-world-war-theyll-be-used-in-part-1-the-set-up/
http://definitivelapseofreason.com/2013/08/11/4-aircraft-carriers-in-the-news-and-the-next-world-war-theyll-be-used-in-part-2-the-war/

Here is his comment/question on that topic :

Hey Tay! Hope you’re well my friend. The nuclear vs. conventional powered aircraft carrier debate is something i’ve been thinking about a bit recently. The justification for not going nuclear on the UK’s QE’s was always upfront costs being higher – typical MOD! I was wondering though – surely this would be offset by increased lifetime fuel costs for a conventionally powered ship? Is this another case of MOD ‘short termism’ or are there other hidden costs in going…