After a lot of faffing around, finally got my Steam Beer going (recipe from Jon Finch's Kindle book on BIAB):
19 litres
3kg Lager malt
1.5kg Maris Otter
40g Halletauer Hersbrucker - 60 mins
15g Halletauer Hersbrucker - 10 mins
15g Halletauer Hersbrucker - flame out, steep for 60...