Fao John Brunton.I am not familiar with this boiler.Does the 40 pertain to 40.000 btu's I wonder?
If so you may have problems putting bigger radiators in and and could excede the capacity and eventually knacker the boiler.A boiler of that size in a 3 bed house maybe only sized for back ground heat.
If you put bigger rads in you may need to increase the pipe sizes and then find the boiler isn't big enough to produce enough heat.
If you go to a heating merchant such as Plumbcenter or Pts you can obtain free of charge a radiator list catalogue,this list included rad sizes and btu outputs.
Do a rough calculation of your existing rads and you will see if you are reaching your capacity,allow 8,000 btu for the hot water 'domestic' and 10% for extreme weather conditions.
Glen., November 2009
