well im gonna be in a somewhat similar situation as you so some decent blokes on the forum gave me estimates on a conversion and its around 10k for a conversion.
I asked Bristol Flying Centre and Multiflight to give their realistic estimates for the flying portion of a license conversion for our students. Interestingly they both came in at about £9,000 to £10,000 all in for a CPL skills test and an IR conversion using a typical number of hours, not the minimum. Details of their figures are on our forum.
the forum link is
http://jals.co.uk/forum/showthread.php?t=148 Also
With my employer you could do 15 hours on the aircraft for about £5145, less if you use the sim for some of it which is about £145 per hour instead of £345. That is about normal for the UK. However, don't expect to pass first time after 15 hours!
hope this helps