We would recommend the PHOTON 100 as a replacement for your Ambirad UF/E 400. Please click the link below to view the product. https://www.reznor.co.uk/product/photon-warm-air-heaters/?selected=9778&pa_kw=2465&pa_fuel-type=2429
What would be a good replacement for a Ambirad UF/E 400?
Looking to upgrade your old heater? Look here for information on which product is the best like-for-like replacement.