In message , Andy Hall
writes

One comment that I would make is that if you are going to go for a
large cylinder and 35kW boiler, do make sure that the cylinder is a
fast recovery type - not just a part L1 model. Otherwise you will
find that during HW recovery, the boiler may well modulate down to
half to 2/3 output if the heat isn't transferred fast enough. Most of
the major manufacturers have these - e.g. Albion cylinders. etc.


RMC Ultrasteel; I believe they are fast recovery.
--
Mark Roberts