Have a look at the Baxi Solo HE.....tried and tested heat ex, very easy to install and no pump over-run so very easy to wire up with no extra wires to run.
Ive been fitting them for about 3 years and have had no bother with them at all.
They are also very reasonably priced.
I concur these are a very sensible boiler and the best value for money on a good deal at MKM and usually in stock.
There are a number of people who like to dis Baxi group but I am not amongst them.
Also consider for utter reliability the Ideal Classic HE band B based on one of the most reliable boilers of recent times.
When I was Alpha service agent if I had relied on repairing their regular boiler range for a living I would have gone bankrupt, since it never goes wrong.
But the major benefits of the Solo and the Classic is that they only require a call for heat live feed, so can replace an old school regular boiler with very little difficulty.
It is not a matter of the popular at any price boilers not also being a great choice, it is a matter that for ease of install performance and longevity the former are equally great choices. There is no need to pay a premium for a regular boiler.
When considering a combi.. that is a big issue as so many have consequenses.
In the past I did quite well buying boxed unused Alpha CDr;s off ebay when people suddenly realised they really wanted a combi. I could fit these with impunity as they never went wrong. though being the service agent was an insentive it was never called upon.
On ebay combis go at a premium because the world is full of people with combi tinted spectacles. But there is an opposite effect of people changing their minds about fitting a regular boiler.
Sadly new price from the merchants regular boilers are a rip off cpmpared to a combi.