You'll have many different answers on this one! Some will say to leave it in the primary fermenter for 3 weeks, some will tell you to use a clearing tank (secondary). Before I started kegging I always used one for every beer. I think it gave me a clearer beer with less stuff in the bottom of the bottles. It also did something really important- it gave the beer some time to age without be drinking it!
I'd leave it in the clearing tank 2-3 weeks before bottling it, and then start drinking it 2 or 3 weeks later. You certainly don't HAVE to, though. That's the beauty of making your own beer- we all can do things a little differently.
Personally, I wouldn't bother on a Mild. It's a small beer, so it doesn't need an especially long conditioning time. That, and I don't really think of most English beers as being especially clear anyway. I'd give it 10-14 days in primary, check the gravity, and if it's done go ahead and bottle.
Generally, I *do* use a secondary, but in this case I don't think it's necessary.
I've got a Mild in primary now. I'm not going to 2ndary it. As Bird said, it's a smaller beer and doesn't need the time that a bigger beer does. I am leaving it in the primary for a little over three weeks, though, but mainly because I underpitched my yeast and want to give them time to clean up after themselves. After that, straight into the bottling bucket.
I don't secondary any of my beers unless I do additional steps like dry hopping or oak additions. I have never noticed a problem with clarity so long as you are willing to stop racking about an inch or so above the trub and lose that beer when racking.
A mild is really designed to be ready to drink quickly and shouldn't need extended time clearing. Most English Ale yeasts used in Milds are highly floccutant and clear quickly.
I say give it 2 weeks in the primary and then bottle. 2 more weeks and it should be good to go.