Peter Woodhouse wrote:
I'm considering a WB combi boiler to replace an exisiting boiler.

Could someone tell me the basic differences between the various series that
they manufacturer.
....

24i Junior

compact lightweight unit different from:

24i
24CDi BF or OF or RSF (or are these the same - different flues?)

Yup, flue options. I think the the i and CDi are mechanically similar
but different controls (clock/programmer?)

The latter types are 'conventional' combis having one gas-water heat
exchanger and a diverter valve & (plate type) water-water heat
exchanger for DHW.

The Junior has no diverter valve or plate exchanger, but both primary
and DHW are heated in the gas-water exchanger assembly. Someone (Ed?)
said Ferrolis are like this too.