2 x Combi Boilers or Combi Boiler with Mega flow?

[AJ SINGH]

Hi All, I'm a novice on plumbing but recently I've made changes to my property and now it has 12 radiator heating with 3 shower bathrooms. As suggeted I went with New more powerful Combi Boiler with 250l mega flow system to support 3 showers at some time (incase) but am struggling with another issue that is, "No Hot Water after 3 or even 2 people bath" (kids do love to spend more time in shower finishing all 250ls).
Now, I've been thinking, isn't it better if there is a way to replace Mega Flow with 2nd Combi Boiler that'll fire up on demand, if that's possible? How and who can help me with this?
Thanks in Advance
AJ

 

[snb]

Sounds like there is a problem with your setup as if correctly plumbed and wired should be able to manage at least 3 full cylinders per hour

 

[ianmcd]

As @snb says sounds like a set up problem your megaflow and a combi should be able to cope with your demands no problem is one of the showers plumbed from the combi ? if when that shower is running the high rate recovery coil will not be re-heating as the combi will put all the heat to that shower