They're ok. I have one ,well a rebadged one a Sabre 35 HE, and had no problems. Pretty basic but delivers decent hot water,toasty hot house and cheap gas bills.
However there were problems with the recouperators bursting on about 35% of my installs which were a mix of Sabre 29 & 35 HEs and some Compact 29& 35 Hes which may or may not have been exclusive to me as Vokera did the three wise monkey act and the supplier I used at the time no longer sells Sabre/Compact boilers.
And,recently there is a known problem with the venturi requiring replacing after about 18 months of use.
Would I buy another Vokera? Nope.
Do yourself a favour and get one of the big three. WB,Valliant or Viessman.
Greenstar 42 CDi is excellent and will give you 17.2 ltrs of hot water an hour provided you have a decent pressure (about 4bar) and a decent flow (20ltrs p/min) of cold mains water otherwise consider a 37 CDi.
tony can i ask did you get that boiler free from a rep for your house?
No. I paid for it myself. But WB do an incentive scheme which I intend to take advantage of in the near future.