Tom, the last detailed breakdown of costs for various options (including different levels of renovation, and outright demolition) that I've seen was from the report released in December 2013, just prior to the vote to demolish. It's available here (PDF):
http://tinyurl.com/zuh3w52An earlier set of estimates was given in 2010. This gave lower estimates for renovation, and a slightly higher estimate for demolition:
https://www.whatdotheyknow.com/request/62501/response/160207/attach/html/9/Minutes%207%20Oct%20and%202%20Dec%202010.pdf.htmlI summarised both sets of costs in a little blog post here:
https://colwynbay.wordpress.com/2013/12/17/pier-demolition/The 2013 report led to the inflated (and somewhat misleading & scaremongering) estimate of £15m for renovation. This "£15m" cost was heavily publicised by the council, and published in all the press coverage. It strongly influenced the vote to demolish. It was misleading for two reasons: firstly, the basic cost (for simple boardwalk renovation) was not publicised. It was only £3.7m. Other renovation options (boardwalk + kiosks, boardwalk + main pavilion refurbishment: £4.1m and £8.9m respectively) were also not publicised by the council. Secondly, the £15m "bells & whistles" estimate included an arbitrary £4m added on for possible "contingency & inflation" (the actual estimate was £11.5m) - an addition unique to this option.
The estimated cost for demolition (£1m) seemed to OMIT all the costs likely to be incurred from what the council describes as the "cons" of demolition. (These costs could be considerable - see my blog post). Make what you will from all this (personally, I think it's a major scandal - a conscious act to misleadingly "slant" public/press perceptions in favour of demolition).
The last I heard of the murals, they were beyond saving. I don't know whether that's been confirmed authoritatively.