A few questions re temp control

[jampot]

Having recently been able to control fermentation temp. I have a few questions. What is best way to control temp. Set at 18c and just leave etc? I have done this twice, both have fermented out well but I notice the yeast head is smaller in size by quite a bit, is this normal?

 

[Dunfie]

You want to let the yeast ferment in conditions that create the best beer. This is not necessarily the same as conditions that make the yeast most active. The size of the yeast head is just a consequence of a different characteristic of your new fermentation regime so is perfectly normal.

 

[Mark1964]

With bitters milds and stouts we usually set temp at around 22 deg c for the first 24 hours or until you can see a good fermentation going on then drop to 18 or 19 deg c

 

[richc]

The temperature you want to ferment at really depends both on the yeast you are using and on what you want the final beer to taste like. Most yeasts you can buy will tell you what temperature range they ferment best at.
To massively simplify things aim for the top of the range for a more fruity beer and the bottom for a more attenuated brew.