I know someone people don't think much of Which? reviews but they found in their Boiler Survey 2021, Vokèra came in second-to-last with an overall brand score of 50%. If one might think Which? got it wrong about Vokera, that means they have wrongly given Worcester too high rating? I've never had any engineer recommend Vokèra but my personal experience of WB has been very good, especially for service. Veissmann came in at around 85% with an overall good review and engineers seem to rate them. My boiler runs well but it has only been two years. The customer support is poorer than WB though.Put it this way, for £700 inc VAT you can put in a Vokera Vibe Max 26C, large bore stainless heat exchanger, larger that the Viessmann, with retarder but no restrictive elbows and constrictions. It’ll modulate to just below 3kW, has dual temp weather comp, OpenTherm, three preheats, wi-fi ready, Bluetooth timer, 5 years warranty or 6 if you pay about £90 for the wi-fi SmartKey which gives remote control of the boiler. You have to buy and register the two together for the extra year.