If so, what would people recommend for occasional DIY use?
Presumably you want a cordless one rather than air powered. The problem with these is that the cheap ones tend to be crap (low torque, bulky, poorly made) and the decent ones are very expensive.
I bought the 24v Clarke impact wrench a year or so ago which was about £90 at Machine Mart, and with a freshly charged battery it's just about ok with wheel nuts as long as they haven't been done up too tight. It won't touch properly tight stuff like crank pulley bolts.
There was a review in Car Mechanics recently, and of the "lower" priced tools the Sealey CP2400 was one of the best performing, but it's quite bulky and heavy so getting to caliper bolts might be a problem. It is very good value at the price I've linked to though.
If you want a really nice one, you'll be looking at least double that price, and up to £500 or more for e.g. the top end Snap On. It's an awesome bit of kit though.
If you have a compressor, the air impact wrenches are cheaper, smaller, lighter and tend to be more powerful.