I've finally got the builders in - need to make final choice re
combi-boiler.

House is medium-large semi, present back-boiler system going in the
bin

I want a high flow system so I can have a decent shower

- the builder's recommended a "Alpha CB50"

http://www.alpha-boilers.com/products/CB50.html

This provides a high flow rate - 18l/min @ 60 degrees C until the
internal 60l cylinder is exhausted, then a flow rate of 9-10 l/min @
45 degrees indefinitely

Is this an ideal system for a good shower? I'm concerned that my
showers are going to be short ones at a decent flow rate.

Would I be better going for a combi-boiler without an internal storage
cylinder, but a high flow rate anyway, perhaps the Baxi Combi 130HE?

any advice would be appreciated

John