answer

I would fit a vaillant ecotec 837. I have run two ex power shower of it. The vaillant is in my opinion far better quality. It has a far better pedigree than any of the worcester range. The only reason to go with the worcester is if it has to be floor standing. Worcester are not the same manufacturer they used to be and are still living on their old reputation.They use too much plastic. I have been called to no end of greenstars with pinholed plastic. You will find the installers with the best reputations in your area fit vaillant. If you must fit a worcester the 440 is there best offering.

The first quote of £4900 is taking the p*** Grit bas by any chance.
 I also would insist on a magnetic filter they make a lot of difference 
to the efficiency and longevity of the system. 
I still think you are better with a vaillant and you'll get a better warranty. Vaillant give our customers 3 years. If you buy the same boiler off who I suspect you got your first quote you get 1.

Boiler quotes

My house has 5 bedrooms and 3 bathrooms and is occupied by both myself,
 my wife and three sons aged 15, 13 and 9.

 Two of the bathrooms are used simultaneously each morning,
but our current 11 year old boiler (Saunier Duval Thelia Twin 28e)
can only cope with supplying water/pressure to one shower at a time
and any attempt to use a 2nd shower

simultaneously, or turning on any other taps results in reduced pressure.

It is vital that the new system meets the following criteria:

- More efficient and reliable

- Cheaper to run

- MUST PROVIDE ENOUGH WATER/PRESSURE FOR
TWO SHOWERS SIMULTANEOUSLY
Any ideas.?

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