We've been thinking about which pic to use for our main wall feature for a while now, after 6 months or so of never being sure, we actually ended up going back to our original favourite and decided to go for it two weeks ago.
A few weeks ago the size we wanted was £101 (42" x 18"), but we stuck it in the basket and held out as Photobox tend to cycle through special offers on a weekly basis. Sure enough, a 48hr BOGOF offer came along just after they dropped the price, so we ended up with two, costing just £35 each...
They look fairly small in those pics, but they're pretty darn vast in reality.
Amazed by the quality, even up close the detail they've managed to retain is incredible. I'm also mightily impressed with how the F1 pic has held up, firstly it was at 420mm through heat haze (I shoot JPEG), secondly it's a crop from this original image (as you can see I've also boosted the colours a bit for the canvas)...
Nothing special was done to prepare them for that size, just a crop at the correct aspect ratio (the files ended up being about 9MB each)
Highly recommended anyhow, thrilled with them.