We would recommend the PHOTON 45 as a replacement for your Ambirad UDSA 043-3. Please click the link below to view the product. https://www.reznor.co.uk/product/euro-t-heating-ventilation-and-cooling-unit/
What would be a good replacement for a Ambirad UDSA 043-3?
Looking to upgrade your old heater? Look here for information on which product is the best like-for-like replacement.