Comet McNaught is now the brightest comet in over 40 years, its reached magnitude -5 (that's brighter than Venus), which means in theory it is possible to see it in daylight.

It's very close to the Sun so it's probably best to position yourself so something is covering the Sun, like a building, but still exposing the sky near it. If you're at mid-northern latitudes it'll be towards the left hand side of the Sun. It's only a few degrees away (just over twice the width of Orion's belt) from the Sun, so it will be hard to spot in the glare.

If you've got a pair of binoculars they'll probably help locate it, just make sure the Sun is covered before you start looking through them. Looking directly at the Sun can cause permanent damage to your vision.

The weather forecast at the moment says 6% cloud for Yeovil at 15:00. So with a bit of luck I'll be able to get some images of it. Hopefully it'll be even brighter by then.

Update: Some pictures posted on Space Weather (their whole gallery is here), this photo by Mark Vornhusen:

Comet McNaught (C/2006 P1) in broad daylight

Update: No luck spotting it here. Got the telescope set up at around 15:45 and ready to roll, cloud then covered the area for about 30 minutes, couldn't locate it in the few minutes before it would have passed below the roof tops. Will try again closer to noon tomorrow, weather permitting but the forecast doesn't sound good with 100% cloud cover.