If your boiler is a Potterton Kingfisher 2 cf100 it was last made in 1998, has a rating of 29.3kW output and a low efficiency rating of 65% - modern boliers are 90% or more efficient.
My boiler has a similar output rating and also drives 16 radiators and a large hot water storage tank.
The UK government are stressing Combination boilers or Combis as being more efficient but if you have one fitted you will lose the advantage of a warmed airing cupboard, a hot water storage tank and the opportunity to back-up the hot water supply, in the event of a boiler failure, with an immersion heater.
Here's a link to a Boiler Buying Guide...
http://www.homeheatingguide.co.uk/boiler-buying-guide.html
There is also a useful link on the page to Boiler Efficiency tables for hundreds of models past and present.
An easier to read table can be found here...
http://www.sedbuk.com/
Your installing engineer will be able to advise you on the correct boiler for your circumstances.
All boilers are good until they break down and the more complex they are the more likely they are to fail.
Good luck...
Peccavi, July 2009