Ah right. I used their website as a way to see the outputs of various boilers on offer.
Many advise to not oversize the boiler, but others imply it should be.
But really, what I want to know is, are the calculators I was linked to earlier, about right for a 1-2 bedroom, stone wall cottage (with dimensions I posted earlier), when they give recommendations of 6.13KW & 6.8KW?