"it was never about having hot water for me, just meaning a little bit of warmth to stop freezing"
Me too matt, ive got a 500l tank and one 300w heater set to 34deg c.,which brings it up to 16deg c. at the top by the morning.( 4deg lower than the legionaires ideal min temp). ive lagged it with a cylinder jacket and old quilt and was out this morning at 8.15. It didnt get above freezing until about 10ish, and was freezing on the sills/ground but no problem with freezing in the pipes. With a bit of common sense as to which props to clean, doors trad, salt (dishwasher not rock) with custys permission,etc and I reckon its not a bad investment at £20.(incl lagging). No need to go any hotter, unless freezing temp get too silly so legionaires not too much of an issue.