Hi Tony, thanks for your reply.
I respect your opinion, however the new boiler has much higher KW on the CH side and quite a bit on the HW side with a much higher flow rate, which I understand will make multiple baths/showers more powerful when used at the same time? That is a step up and a new boiler with a ten year warranty can't be a bad thing? The Vaillent will need replacing in the near future surely so why spend money on it I can put toward a new and better boiler? The heating in the house isn't particularly great with the Vaillent at about 18KW I believe so 35KW should heat the rads up faster right?