I can concur with Alex. As a person dealing with people converting from FAA to JAA on a daily basis and seeing about 20-30 already complete this conversion this in 2005 I speak with some experience.
You costs are way off ! Be a lot more realistic with those prices, they are too low, and like I tell all people wishing to learn to fly its extremely rare for a person to make it through a course in minimum hours. I have seen FAA to JAA IR conversions take 40 hrs for a low time FAA pilot, which you will be if you follow your plan of attack.
Remember too, as part of a DL ATPL course there are mandatory pre exam prep courses that must be attended, so these need to be factored in, as well as accom and food costs during your times at the exam center ( unless of course you live beside one!) .
Have a better search through PPrune, and contact a couple more flight schools about the conversion, try and talk to schools who have actually put students through the conversion, or better off come and see us all at the Flight Training Show on March 19 at Heathrow!
Chris