Our 25-yo Netaheat suffered a fault last night. It turns out it's the
fan and we decided to have it fixed for one last time.

My very friendly installer only does the Vaillant 831 and the
Worcester-Bosch 30Si, and as I would prefer to use his services, I
thought I would investigate. If I read their specs well (I could not
find much on the Vaillant website) they are pretty marginal for my
property (3 bed detached, 2 baths, Scotland; the W-B site recommended
the 42CDi or the Highflow 440CDi), but let's not dwell on that.

When the time comes, I would like to get something that will last, is
proven but reasonably state of the art and is good value for money. In
terms of cars, I would buy Honda post face-lift, not Rolls, nor Lada
and I buy used.

Back to boilers, in terms of features, I (think) I would like weather
compensation, for example. Also, they both appear to modulate, but who
can tell how low they modulate? I also (think I) would like stainless
steel exchangers; have these got them?

Importantly, how reliable are these? I understand they are pretty
popular brands, so spares are unlikely to be a problem. And that's a
big thing; I had a look at Broag (hail Dr Drivel) for example and they
don't appear to have installers north of Hadrian's Wall.

Thanks in advance,

--
Kostas