In general, though the exact details varied across breweries, fermentation took place between 60º F and 70º F. Very strong beers were often pitched a degree or two cooler, but had a similar maximum temperature.
The exception being, of course, the handful of specialist Lager brewers, like Barclay Perkins. To take them as an example, fermentation were between around 45º F and 55º F.
Despite what you may have been told, Scottish brewers didn’t ferment at near Lager temperatures. As this fermentation record for a William Younger Mild Ale.
|William Younger 6th August 1941 XXX|
|day 1 AM||65º F||1030|
|day 1 PM||66º F||1027|
|day 2 AM||68º F||1020|
|day 2 PM||69º F||1018|
|day 3 AM||64º F||1015.5|
|day 3 PM||57º F||1015.5|
|day 4 AM||56º F||1015|
|day 4 PM||56º F||1015|
|William Younger brewing record held at the Scottish Brewing Archive, document number WY/6/1/2/78.|
It looks like the wort has been allowed to heat itself for the first two days, before the attemperators were turned to drop the temperature down to 56º F. This is a pretty typical fermentation profile not just for William Younger, but for other Scottish brewers, too.
The process at Barclay Perkins was generally similar, with the yeast pitched at a little over 60º F and hitting a maximum temperature of around 70º FL
|Barclay Perkins 11th April 1941 X Ale|
|12th April 9:30||64º F||1028|
|13th April 8:15||70º F||1014.5|
|14th April 10:00||70º F||1008|
|17th April 11:15||59º F||1008.5|
|Barclay Perkins brewing record held at the London Metropolitan Archives, document number ACC/2305/01/624.|