My husband finds it very difficult to find longs/bibs to fit (he's a sprinter). So we ordered about 12 pairs in one go from Wiggle (honestly!) - he tried them all on & found that the Endura ones fitted (it works really well having lots of pairs at once to compare). We then returned them & got credited within a day. We probably ended up trying on many more than you can get in any one shop & it was a really efficient way of doing it.
I find Wiggle in particular are great about returns & credit you really quickly - they also have a good range. I think their policy probably works quite well as I often order things from them secure in the knowledge I can easily return them.