This has been my worst year ever for wasps. Fortunately my hives were strong enough to deal with the problem invaders and this is the crux of the issue. Weak hives will likely succumb - uniting and/or minimising entrance helps a lot.
The easiest and cheapest method of trapping suggested athttp://www.beekeepingforum.co.uk/showthread.php?p=506805#post506805 above is very practical and cheap, if not virtually free. I prefer a mixture of raspberry jam and water (wasps just love raspberries whereas bees aren't interested in it) in the lower part and then staple the inverted top section to the bottom part and place it in old "kilner" type jars to stop them being blown over when in situ. I have never found putting them quite near to the hives a problem, despite all the no-no warnings by other posters on this forum. In fact some were under the OMF to stop dilution by rain. This was so effective that I had to redo the traps after a max of 2 days in the beginning and got thousands of the blighters. Third time and the numbers dropped enough to enable removal.
KISS principle here imho.