I've got a load of titles that I want to apply the same effect to (something like a slide direction blur), I've been poking around to see if I can create the effect on a clip, then replace one title with another...
You can do this. Copy the title with the applied effect, paste it elsewhere into the sequence, and then hold down the Alt key as you drag the replacement title on to the pasted title. The effect will be preserved, but the clip will be replaced.
OR copy and paste all the clip attributes (including position and transparency)
You can do this, too. Select the clip with the effects in the sequence, either press Ctrl+C or go to Edit > Copy to copy the clip, select one or more target clips, and either press Ctrl+Alt+V or go to Edit > Paste Attributes. All effects and transformations will be pasted to the target clips, without changing the clips themselves.
OR create a preset that contains all the effects...
And you can do this, as well. With the Effects Control Panel open, hold down the Ctrl key and click on the names of all the effects you want to include in the preset. Click the flyout menu (it's the tiny four-stack of pancakes at the upper-right corner of the pane) and select Save Preset. I'll let you figure it out from there
Ideally the solution would enable me to change the effect and update all the titles. Is there a way?
No way to directly do this; any effect or effect preset applied to a clip is an independent instance, and is not connected to the original in any way. However, you could use the preset building process I outlined above to semi-quickly update all your titles. If you've applied an effect or effect preset you don't want any more, select all the clips that are thus effected, and right-click on one of them and select Remove Effects. Tick the options that you want to remove. Then, rebuild your preset, and apply it to your clips again; you can apply a preset to multiple clips by selecting them all and dragging the preset from the effects bin. It's a little bit of a round-about way, but it's about the quickest it can get.
Another similar way would be to apply the Effects to one Title. Rt-click and choose Copy. Then use Ctrl+click to Select all necessary Titles and then Rt-click, choosing Paste Attributes.
Thanks colin for an excellent in-depth answer!!