Or you could do it yourself.
We did it for my exes 30th, did up a barn with fairy lights and comfy chairs and had a bonfire outside and fireworks, it was fantastic.
Loads of people came down and spent the day getting everything ready and preparing salads and other nibbles and it was a great atmosphere. We roasted the hog throughout the day and finished up sitting round the fire with the lovely smell of the hog roast drinking whisky :)
It may be harder to do this with a wedding though, or if it's not on your land, could do a prep day the day before maybe and get someone to look after the roast during the day and get everything ready.
Lot of work though especially with a wedding as well.
There are some hire sites eg...
http://www.spittingpig.co.uk/?ppcdet=google&pp cuser=13&gclid=CKz8x8uPyYgCFQpQEQodQQocBw
http://www.sizzlinghogroast.co.uk/
http://www.hog-roast-direct.co.uk/online/form. php
http://www.goodfoodcatering.co.uk/index.html
Somerset -
http://www.olishogs.co.uk/
Chepstow -
http://www.onecallcaterer.com/
Scroll right down here and there are loads at the bottom...
http://www.event-management-uk.co.uk/links.asp ?cat=hog%20roast