"mark" wrote in message
...

Planning to replace my old combi with a new boiler.
I plan to use a Vaillant Ecomax 635e system boiler hooked up to a 250litre
unvented cylinder.

Avoid an unvenetd cylinder.
http://www.waterheaterblast.com

You also need an annual service for an unvented cylinder and that
cost...just to store a cylinder of hot water. Fit a heat bank. Same price
but better all around...and safer. Do a google on this groups and
"Pandora".

The boiler is good. Try the Glow Worm condensing range. Vaillants inside
(same company) but cheaper....and very quiet.
http://www.uselessenergy.org.uk/boilers_prices.asp

Im thinking about using a weather compensator:

http://tinyurl.com/qre3a

Anybody got one?
Any opinions on how good/bad/indifferent this boiler is?

The weather compensator is worth it. Also zone off the CH upstairs and have
a stat/clock on downstairs and upstairs. That will save a hell of a lot of
gas not heating parts of the house unnecessarily.